First off, I hope you got medical treatment for the tear. It's not like other wounds, as it is difficult to keep the area clean and you can't exactly put a bandage on there. It is possible that you have scar tissue, so ask your doctor. And believe me, doctors have seen and heard EVERYTHING. Your doctor will not be shocked, and s/he is obligated to maintain physician/patient confidentiality, even for minors.
So go - even if you have to tell a fib and tell your folks that you're getting headaches. You should go.
Now, for the rest of it.
Some people are better at sex than others. Skill levels vary, as do proportions, etc. Foreplay is often key. Fellows who don't spend a lot of time on it may not be stimulating you enough with just intercourse. A dirty little secret out there is that a LOT of women don't orgasm with just intercourse. You may be one of them. And there is not a thing wrong with this. It's reality, and it's common.
So, what to do?
Have sex with guys who care enough about your orgasm to be a part of it. And who have healthy enough egos that it matters less to them if you orgasm from intercourse or oral or digital stimulation or porn or even, hell, dancing the polka, than that you have one.
You'll be fine. But you should see your doctor, and not just about the tear. You should also see him/her about birth control.