really worried anyone got experiences or good advice on this.?

I am really worried and possibly over stressed I went with a guy whom I known for ages we have had sex three times in the space of three months two times being protected and the last time unprotected.. the dates are as follows to make story brief...

10th June had protected sex panicked took morning after pill one hour late bled at my normal time for a period between 17-20th June. (took std full test on 25th June all came back negative)

26th June had protected sex panicked again took morning after pill 14 hrs. later had a bleed a week earlier than expected for normal period from 10-14th July all normal (also did std tests again 10th July and all negative)

21st July had unprotected sex and took morning after pill 1 hour later had a bleed one week later only for 2 days 29-30th.

took a pregnancy test 19 days after the last incident which was on the 9th august came back negative.

also had symptoms of a uti infection on the 3rd august when doctor dipped urine he said urine infection gave antibiotics symptoms went and came back the symptoms are frequent urination no pain and just pressure on pubic bone.

on 6th aug did a std test again has come back negative went to doctors yesterday he said he send off urine to see what bacteria has done swabs for std to be sure but he said by now it should be positive.

if no uti is found then what is causing my symptoms?

do I need to do another pregnancy test?

do I need to do another std test?

could stress be causing this?