Does my boyfriend have low T?

My boyfriend and I have been together for 2 years and he's always been less interested is sex than I. Things have improved after numerous arguments, but he still just isn't that interested. He is at times, but also has trouble keeping an erection sometimes. He said he would see a doctor but hasn't yet. We have a great relationship and everything else is great. I feel that I am a very desirable woman, but sometimes I just can't help but feel like it's me. Help!