I don't know where to put this

Hi everyone, me and my partner have been trying for almost a year now, I have 2 children from a previous relationship first I fell pregnant on bc and 2nd was planned and fell pregnant the 1st month of trying. I split with him 3 years ago and a year later met my current partner who is amazing, I never thought I would have anymore children but seeing how he is with mine changed me and he wants a baby soo much and honestly I can't wait to make him a daddy. the only problem is I know I'm very fertile from previous tests, I think it maybe that he might have some trouble but I don't know how to tell him? it's such an awful subject how would I bring this up with him? please any advise would be helpful