Why do I get thrush everytime I get my period?

That used to happen to me, it's caused by the drop in hormones. I just used Caneston cream to stop the soreness, and occasionally would take the 1 pill if it got too bad.
Don't take the pill every month as your body will get immune to it.
UK

What products do you use on your period?

Remember commercial menstrual products like commercial pads such as Always will increase risk of infection by preventing air-flow and ingredients in the pads can cause irritation, tampons are also a major cause of vaginal infections due to their impact on vaginal flora - try menstrual cups, softcups, period underwear, cloth pads, or even just organic cotton tampons and pads to see if they make a difference. Also be aware of any cleaning products you're using, many people will use things like wipes on their period or use soaps to clean as they think menstruation makes them 'dirty' (hint: it doesn't), this can of course also lead to irritation and infection.

Ask your GP.