Confused..

Hi everyone, I love reading your topics as they have helped me out a lot so far, but one thing I am still confused about is knowing which day i ovulated. Is my peak day the day i ovulated? If so that was the 19th meaning I would be 3DPO. And also, my boyfriend and I are TTC so we had sex the whole fertile window and now I am feeling some pressure in my lower abdomen, not like cramps but it just feels like someone is pressing on my lower abdomen and I get nausea in the morning and off and on during the day. Is this normal? Anyone else have or having these symptoms as well? TIA!