Still not conceiving?

Star
Me and my boyfriend have been trying for 8 months now and still no positive?!
​I get so upset when I come on my period, because I will be late for 5 days then just come on after getting my hopes up. 
​I am only 19 and have been told that being this age has an even higher chance of conceiving but still no luck! 
​I have been pregnant before in my early teens and went through with a termination as I was only thirteen years old, but now I can't help but feel hurt by what I did and now I want one and have been trying I can't fall pregnant? I feel like it's karma for what I did when I was thirteen. 
​Sometimes I think It might not be me and that it might be my boyfriends sperm, but with my ex we were trying for over a year and nothing? :(