You should definitely see your ob/gyn. I am 19 and had very similar problems to the ones you have explained. For months I was having tests done and trying many different types of medications. They wont do a hysterectomy on you. Youre too young. And no, once you get a hysterectomy, you dont have any more periods. They take everything out (uterus, ovaries, fallopian tubes) for a complete hysterectomy making it impossible for you to have children. Your doctor can give you medication for nausea (metoclopramide works wonders) and may do a D&C. Best of luck!
You'd be better off going on a birth-control pill that reduces your periods. I also don't think a doctor would do a hysterectomy on an 18-year old. It is also possible that you have a uterine polyp that has this effect, and those are easily removable. See an ob-gyn and get some diagnosis -- maybe an ultrasound or an MRI to rule out polyps or fibroids -- and to talk about various options. I would be leery of ablation if he suggests it, because it means you could not have kids safely later, but I'd be open to any other possibilities, including a D&C to remove any interior growths in the uterus, or putting you on a pill that will reduce the periods. In the meantime, Advil and Nuprin are antiprostaglandins, and help a lot with cramping during the period. (Better than Tylenol or aspirin by a long way.) Good luck!
I don't see a doctor letting an 18 year old girl get one. Have you talked to your Dr. about these issues you've been having?