Trying to conceive....

My bf and I are trying to have a baby , but it seems like it isn't working. I map out fertile days and have sex then. Its been 3 months since i removed it(paraguard)/been trying and nothing...BTW I was on paraguard for almost 7 yrs (do u think this is the problem) I never had a problem before i have 3 children. He feels like he will never have a kid or maybe can't have any...his past wife cheated and said it was his baby, but wasn't after all. So can anyone give me tips on what we may be doing wrong?