Bad internal ultrasound experience age 15

So I've had my period for 4 years now and I still can't use a tampon. At the beginning it just hurt- A LOT- to even try a light sized tampon. Now I'm worried that I have a bigger problem... Last year I went to the ER for abdominal pain. The doctor refused to believe that I am a virgin and sent me for an ultra sound. I being 15 (I'm 16 now) thought ultra sounds were only the external thing you see on pregnant women on TV. Man was I wrong it turned out he ordered an internal ultra sound.  This did not go in and the nurse just kept trying to jam it in. Eventually she gave up.    Now any time I try to put a tampon my vagina gets really tight and I freak out. It's even started happening when I'm cuddling with my bf and I have to get up and leave the room to calm down. I don't know what to do.   Any suggestions or similar experiences?