Hi, was your period normal like your past periods? If so, you are most likely not pregnant.
Hi there. Well, I want to tell you first off that peeing after sex does NOTHING to prevent pregnancy. You MUST use reliable birth control if you are going to have sex each and every time. You can get pregnant at any point in your cycle although certain times are more likely than others. The day before your period is questionable. It is not a likely time but never say never. Breast and nipple changes are not unusual for PMS.
The symptoms that you describe before your periods are very normal.
Sometimes around 10 days before a period you may notice your breasts and nipples sore and tender to touch; you may notice bloating; fluid retention; you may get very moody and irritable; you may get cravings for certain foods - usually sugary ones and chocolate. You may experience a few days before your period starts pain in the belly or lower back.
All the above symptoms are classed as Premenstrual Tension, sometimes called Premenstrual Syndrome.
Eating a well balanced and healthy diet and cutting out or cutting down on sugary, junk and processed foods and drinks and eating more fruit and veg, will help curb your symptoms as will taking Evening Primrose Oil.
Eat seeded brown bread instead of the processed white bread, cut out cakes, sweets, fizzy drinks etc. Drink more milk and water.
Having sex at the start of your period and your period coming on as normal, personally I would not about any pregnancy.
The reason for your nausea is likely to be from worry and stress or from having eaten or drunk something that has not agreed with you.
As you wrote your post on the 28th you are either still on your period and nearly finishing your period. It would be far too soon for you to get any symptoms of pregnancy like nausea so soon after having sex. Pregnancy symptoms usually present themselves at the 6 to 8 week of pregnancy.
Some women on the other hand, can still have a bleed whilst being pregnant. The bleed would very likely be different from your normal menstrual cycle.
The nausea may be part of a stomach bug. If that may be the case, avoid eating and drink all dairy foods until you feel well again. If your symptoms persist, make an appointment to see your doctor.