Please help.....

So the first of the month I got a uti they gave me one medication took it for 3 days & it made me sick so doctor called me in a different kind of medication & I took it for a week the app said I'm suppose to O the 8-14 well I started O the 18 and AF was due on the 27th so I'm now 4 days late so could I be pregnant? Or is my af going to come later due to being on the medication? I never notice my CM until this month and it was very noticeable so the app could be completely wrong for when im suppose to O im having tender nipples and im extremely tired. last month AF was 3 days late... please help I'm just hoping and praying we are pregnant