Depo?

Sondora
Ok so I had a baby in May, and in June I got my first depo shot. My husband and I both are financially set and have always wanted a large family with siblings close together. Anyways I only got the one depo shot and I never went back for any others, I was due to get my 2nd shot in September, but never did. We discussed things and felt like it would be ok if we were not exactly "preventing " a pregnancy in the end November, infact we have pretty much been TTC because we are not using any form of BC or condoms and he only pulls out sometimes. That being said I randomly take pregancy tests just to see if anything has happened because I can't rely on my period dates due to the fact I've always been extremely irregular, is it strange that we haven't had a positive test yet? I know this may sound rude but we had no trouble conceiving our first child and I'm kind of worried  that I may not be able to conceive now because I got that one depo shot, is that even a considerable concern or should I just relax?  Any opinions would help! Thanks.