Should I be worried?

If I have an irregular period, but it regulates every now and then, but then messes up again and I have been under severe stress but I had sex on November 4th, and October 24, and got my period later in November. I'm not pregnant am I? I'm just skipping due to stress? Also, my partner did not ejaculate, either of the encounters, and wore a condom. I'm only worried because I'm late, and if I don't think about the thought of being pregNant, I feel fine but if I do think about it, I start feeling sick