Morning after or should be ok?

My period ended sunday/Monday (monday was mostly just the brown discharge rather than actual bleeding) and last night/early this morning my partner and I had an oops. According to this app, i should not ovulate until next Wednesday and it says my fertility is low for the next 3 days. Im not overly worried as tracking my cycle has always been pretty accurate, but im in a new relationship and both my partner and i have teenage sons from our last relationship and neither of us want more kids, last night was actually our first time together as we have been in a long distance relationship for the past 6 months and finally met a few days ago (I'm from the US and he lives in Spain, which is where i currently am) we are both older so probably less fertil than in our younger days (im 37 and he is 51) but i know it's definitely still possible. Im really worried about the side effects of taking the morning after pill because my body has never done well with synthetic hormones but obviously i also dont want to get pregnant either. Im torn on if i should risk the side effects of the pill or risk the possibility of pregnancy.