Freaking out about the possibility of being pregnant?

I understand if I'm worried about getting pregnant use a condom, I usually do. My SO and I ended up getting drunk and having sex (didn't even think about a condom at that point) he pulled out but was a bit late. My LO is 14 months old and I don't know if I'm just imagining things because I'm freaking out or if I could actually be pregnant, my period is due in 10 days so I can't test yet, having another baby could screw up our lives completely at this moment so it's been something I've been trying to avoid. I have a thyroid problem so I have slimmer chances of getting pregnant (so they say) but I've been so nauseous lately, my stomach hurts and everything else, ugh.

I guess this is just mostly a rant to get it off my chest since I don't want to bring it up to him because of the potential to ruin everything we have planned for our futures.