No one to speak too

I thought I would write on here because I need some advice from another woman and from someone who won't tell me what I want to hear. I am in my twenties and TTC. In October 2013 I had the depo jab I should of gone for a top up on January 2014 but I missed as I want to try for a baby now. Since then I have had regular periods, I do ovulation tests throughout the month and they come back positive. I have been too doctors and had tests done they came back as I'm fertile. I've cut down smoking and when I'm stopping it. But im still struggling to conceive. My periods come on the dot so I haven't even had a pregnancy scare. I am now taking cassanovum to see if that works. From all what I have said do you think it is my partner that is infertile. He has got children from a previous relationship. When I say your sperm must be dosile or low he says well I'm fertile...its not me. So more than likely he won't get checked. But I deep down know that it's him..so I don't know what to do. This little journey in my life with the TTC is such a nightmare I thought it would be fun but its just tears. Don't know if to just forget having a baby