Having the signs but when and what do I tell him?

My bf of 3 years and I broke up in the beginning of July. Two weeks later he began dating another girl yet he cheated on her with me. We had unprotected sex. I've had pregnancy scares before and all were negative so this time I didn't worry about the possibility. Well...I've been having many of symptoms of being pregnant. I am on the pill for endometriosis...a disease where there is a lack of endometrium in my uterus which is very painful. The pill helps ease this. Before I even had sex I hadn't been feeling good down there as if maybe my pills weren't working this month...I've heard of it happening. I think there is a great possibility that I'm pregnant but it's only been a week and I've just started all these symptoms: nausea, puking, constipation, EXTREMELlY tired, headaches, and VERY bad mood swings. I don't know when I should mention these things to my ex. I think it's best that maybe I wait another week and take a pregnancy test if the symptoms remain...if I'm positive then I'd tell him but only him and my best friend. I'm also scared that I could lose a baby since of my problem. If anyone has been through a situation like this or can help all advice is GREATLY appreciated!

when exactly ( whats the date) you two did it?

time sequence means alot here.

if it was within 2 days, there is hope for EC pills. (morning after pill)

we had sex last Monday almost a week in the morning.

ehh.... you're out of luck then.