Why cant i get s anymore?!?

I am 16 years old and for the past 3 months ive notcied i do not get s like i used to as easily. This is ridiculous,im so ******* frustrated about life now. I have a new girlfriend and for about 3 months now and she even went down on me and i couldnt even get hard fully within a minute. I really had to make the excuse up of me saying i was high before i came to her house.i really hate my life because of this ****,im so close to thinking about giving up on everything and killing myself. why do i got to be so different than all the other 16 year old guys out there?i lost my cirginity a long time ago,but i just do not get hard when we make out or anything anymore. I went to the doctors because i had minor pain and they found out it was a varicose vein in my left testicle. The docter said its nothing to worry about and it doesnt cause problems with getting s.is this true?I dont know wtf to do anymore, I feel like quitting everything in life. I feel like such a dumb, I love my girlfriend deeply, We used to go out 2 years ago and we decided to try it again this year.We wanted to take the relationship to the next step by having ....and now look what this **** got me. I hate my life,please....someone help me. Give me someone to talk to about this, AIM or Yahoo Messenger would be best. Serious advice only please,Im so close to just ending everything