Does anybody know what causes to be dizzy?

I have been getting dizzy lately it happens randomly. I could be driving or laying down idk what’s wrong I’m low key scared. And no I’m not pregnant. I have the IUD. I drink tons of water. I stay active all the time. Can it be stress or something worse? I started getting dizzy with my second pregnancy and it was the first two months it was the worse I almost passed out one time. My baby is now 7MO and even after labor and having my baby there’s times I still get dizzy? This has never happens to me before. That’s why I’m kind of scared of what it could be or what I could have? 😓