might be pregnant...

So I'm currently 5 and a half months pp and today I had to call my nurses hotline for not feeling great. I pull out my medical card (that apparently I haven't looked at in 3 months) and seen my date for my next depo shot.... I'm almost a month over due for the shot. I feel so irresponsible right now. I have some very good reasons to think that I'm pregnant too. Haven't taken a pregnancy test yet. Anyone have kids this close together and feel sane? To add to all of this I made a joke like "what if im pregnant?" He did not find it funny. He almost seemed irritated at me even joking about it.