help with TTC

Me and my fiancé started trying for a baby in march and as to yet we have had no joy 🙁 when it got to the 6th period mark I had a little break down and told my partner that we will "stop trying so hard" and what ever will be will be. I got my period last weekend and i was devastated. Iv tried taking conception tablets but they put my cycles all over the place. I take folic acid and eat relatively well. I'm really at a loss and I feel like this is never going to happen. I already have a 7 year old and I'm super blessed to have her. I'm really debating on whether to just give up as it's hurting too much and just always be grateful and blessed knowing I have created a beautiful child. My fiancé just wipes away my tears every month and says it will happen when it happens but I feel like such a failure that I can't bring him a child of his own. (My daughter is to a previous relationship) any advice and help would be great. Thank you xx