Major advice

Period was March 15-19 I had intercourse without a condom March 26 then a condom on March 27 although  we didn't start off with one in the beginning just kind of at the end which was pointless... Still considered precum both days were two days before fertile window opened, for the past two weeks I've been super tired, nauseous, in a mood that's unbelievable. And urinating every five to ten minutes. Then on April 2nd I had sex on ovulation day would there be any chance of pregnancy? I tested for all sexual transmitted diseases and all diseases at that all came back negative! What could this be? I'm not stressed or anything and I'm in great health..