Yeast infection

Hi all! So I think I’m starting to get a yeast infection again I had one just before Christmas with my last time having “sex” on the 17 December. By “sex” I mean his penis was in me for about 10 seconds & no ejaculation. I’ve had a real irregular period lately and it has still not come but I have not done a test..

Can anyone tell me why I’m all of a sudden getting these?