What Is The Cause Of Pressure Sensation In Abdomen And Heartburn?

My boyfriend and I are in our late 20's (28) and have been together for 3 years. I usually have a 28 day cycle which never goes beyond 32 days. I'm currently on day 34, still no period, and had 2 negative pregnancy tests. Other than pressure in my lower abdomen and heartburn, I have no other pregnancy symptoms. I keep track of ovulation by monitoring my physical signs which occurred around the 14th of January. We practice the withdrawal method (and I know he does not slip-up) and sessions are not consecutive so there is no sperm left in the urethra to be picked up by pre-ejaculate. On day 27, I allowed him to ejaculate inside me because ovulation occurred about 2 weeks prior and thought the chance of conception was extremely low. I had the flu for 2 weeks that started the same day as my period and also started taking supplements (Oxyelite Pro, Magnesium, and Calcium) and cough/cold/flu medicine that contained acetaminophen, dextromethorphan, phenylephrine HCl, and doxylamine succinate. Due to being sick and then going away for a week, we barely had intercourse in January (only about 4 or 5 times total). Is it more likely I'm pregnant or more likely the combination of supplements and illness is just throwing my cycle off?