Please tell us either the actual notes that are causing your throat to hurt. Use your guitar to determine your range. I'm sure there are articles here to explain how to do that. Post your range here, or tell us some familiar songs that you can and can't sing. Start in the middle of your range, which is usually close to the same pitch as your normal speaking voice. Find a well-known song in this range, and see if you can sing it with no strain. For example, if the middle of your vocal range turns out to be baritone, then find a song such as one from Depeche Mode, and practice it until you are ready to record it. Then, put it up for us to hear.
First, do not sing notes that cause your throat to hurt. That higher part of your voice will become available once you have learned and practiced all of the basic techniques.
My first guess is that you don't have proper breath support yet. I haven't looked yet, but I assume that there are articles about this in here somewhere. Like open-throat, it is a very basic skill that everyone must learn. Lack of breath support will make you pitchy, "light", and your notes will sound like you are talking with a weak voice. Right now, that is what I am hearing in your voice.
Breath support starts with taking a proper breath. When you go to bed tonight, just lay there and allow your entire body to get relaxed as possible. Clear your mind, then focus on your breathing. Almost everyone breathes properly when they sleep, but many people don't breathe properly when they are awake. You can do this while lying on your back or your side. Once you are completely relaxed, your breathing will naturally slow down. At this point, most people are breathing properly. As you begin to inhale, you should feel the sensation of movement very low in your belly, and it should feel like "something" is descending toward your crotch. That "something" is your diaphragm, a muscle that is attached to the bottom of your lungs. Your lungs are just bags that fill up with air when the diaphragm pulls them down. When you are relaxed, the diaphragm's job is made easier. That's why people are always saying, "Just relax, and take a deep breath." Now, begin to take deeper breaths by "pulling" those sacks of air (your lungs) even lower. If you can do this, then remember to celebrate when you get up in the morning, because you have made a breakthrough.! Congratulations! This technique is called diaphragmatic breathing, or belly-breathing. But, we aren't done just yet. You must be able to hold this position while you vocalize a phrase, release it to exhale during your rests in the song, and inhale and hold again for the next phrase. As you vocalize, allow just enough air to make your vocal cord flaps move well enough to fill your open throat and mouth with a vowel sound. Again, use "aaah"s and "uuuh"s until you understand and learn through practice how this feels and sounds. Don't be discouraged if it initially sounds crappy. Just practice, practice, practice. Stay in your mid-range, and do an "aaah". Sustain it for a few seconds. If it feels good, then work on sustaining it a little longer. Stand up straight while keeping your neck and shoulders relaxed. Keep your head level, your chin in a neutral position. Watch yourself in the mirror when you are learning and practicing to make sure that your head and body are actually doing what you think you are telling them to...Now is also the time to start working on how to end each and every phrase you vocalize. This is one of those techniques from which beginners can benefit. Also, remind me to bring in vowel shaping and modification (you used it improperly and probably accidentally) later...
Basically, the key to ending a phrase is breath support. Most beginners have plenty of breath, they just don't realize the importance of ending each phrase as strongly as the beginning/middle of that phrase. Pretend that you are singing in a small but loud, crowded nightclub. Your mike is just strong enough to reach the guys playing pool in the back. One of the guys is a local record producer for an independent label with major connections in the biz. You don't know that, which is actually my exact point. When you sing in public anywhere, you need projection that reaches everyone in hearing range. I am not talking just about power, but projection of your voice to your listener. What I am talking about is actually kinda border-line ventriloquism in the sense that you are placing your voice in the surrounding area. When some people start learning to sing by singing along with their favorite songs, they rarely, if ever, have sang outside of their shower (best reverb in the world, and the water fills your ears and drowns out how bad you are)...
So, project your voice powerfully and steadily all the way through the phrase to the end of the last note. Your trying to sing, not talk. Listen to REO Speedwagon to hear how to end phrases. Not all singers do it this well, but the best pros do. Some beginners tend to be soft on the first and last note, and they sometimes don't even recognize that. You hear it on the attack of the first note of the phrase and again at the end.
I seem to be drifting into deeper waters here, so I will quit right here! LOL I probably lost you already, huh?