Trying for almost 3 years now

K
Hi ladies, I just wanted some opinions. I am 20 years old and my fiancé and I have been trying for almost 3 years this August. I will be 21 in July. I found out I was pregnant back in October of 2013 and we were delighted, but it ended in a chemical pregnancy. We have been trying so hard, using opk's every month and making sure we make love on my fertile days. It took till this year in January to get pregnant again. It also ended in an early miscarriage. As soon as I found out I booked an appt for the next day and my blood levels were at a 14 and they eventually went back down again. I am so confused and I am so depressed as to why I can't stay pregnant and it takes so long to even get pregnant. I have very regular 32-35 day cycles and every month I get positive ovulation tests. (I use clearblue digital) we have also been using preseed since January of this year and so far nothing. I am going back to my obgyn in August. But this is driving me crazy. I am overweight so I don't know if that has any effect. Not sure why since I have regular periods. I really want to try herbal remedies but I don't know where to start or what would suit my needs. What do you ladies think? 
Have a blessed day and baby dust to all of you.