18 with erectile problems

Ive been having erection problems for about a year now. Before this i used to be real exicted about meeting and having sex with women but ever since this started i have had no desire like i used to. I have a girlfriend we have been dating for 6 months and i have been having trouble maintaining an erection with her. This started last year when i went down to virginia. there was times when i used to be really aroused and i would masturbate to homosexual porn. i never thought of my self as gay but it would get me more aroused then females at the moment. I never had a crush on a man or anything and this thought of me being gay causes me to have intense anxiety to the point where i dream about it or i cant sleep at all. i dont want to be gay but the thought always pops up into my brain but i remember it wasnt always like this. I just want to go back to me liking girls the way i used to