Light period 3days then heavy 2days??

Hi i'm wondering if anyone can help. i am on the pill & 3weeks before my period was due i had a 24hour bug of vomit & diarrhoea. The night before i had the bug my partner and i had sex. So all month i was convinced i was pregnant, i was bloating a lot & close family & friends were pointing it out. Anyways it came the day my period was due it always comes like clockwork this was no different it came monday really light nothing tuesday light weds. Normally the first few days i am in agony my cramps are that bad i don't know whether they are period cramps or if i need the toilet so this was very strange.. Plus i had carried on my pill the previous month to skip my period so i should have been getting this period twice as bad.. So i took a hpt the weds & it was neg the thurs & fri then i got a heavier period not like usual no clots but still heavy. I know about implantation bleeding but none iv read sound like this. I'm wondering has anyone else experienced anything similar or am i just being paranoid.? Thanks in advance