Why am I having such a hard time?

Hi, I am 25 and TTC my second baby. My daughter is 5 and I got pregnant with her on my first try. Now, my boyfriend (27) and I have been TTC for 8 months now and nothing!!!! My daughter has a different dad. Is it my boyfriend? Or me? Ive had tests done which revealed everything was normal and I am ovulating. My periods are regular and I am healthy. However, my boyfriend does not go to the doctors, he is kind of overweight, he smokes weed a lot (more than my liking), and he does not really take care of himself (exercise, diet, doctors, ect.) would those factors have something to do with why we're having such a hard time? I've tried to talk to him but he doesn't seem to be making any changes unfortunately. Any advice?? I have a semen analysis slip from my doctor he just has not done it yet.