Do I have erectile dysfunction? Please help!?

Hi, I am a 25 year old male. I have high blood pressure (140/100), especially at night, I smoke cigarettes and that may be the cause too, but something may be wrong with my , I don't know what to do, I try and try to have with my girlfriend and just as I am about to enter I go from completely hard to completely soft, also it seems like I can only stay hard when I am very close to reach . I do wake up with s about every other day. I always try to satisfy her before attempting to make but she prefers the , so we end up sitting there wasting condoms because I keep going soft, don't know what to do, can anyone please help?