Why am I bleeding before my period starts?

Since June I’ve been having on and off light bleeding almost like a mini period a week before my main period comes. Sometimes it’s just red ish discharge and other times it’s just light bleeding.

I’ve Never had any issues like this or spotting before it feels to much to be spotting. And it’s really starting to get on my nerves now. (As it’s inconvenient and nobody wants a 2 week long period)

The only reason I’ve not gone to get checked out is cause I’m not in any pain and I feel like they’ll just chuck me on birth control which I don’t want to do.

Any other ideas as to why this could be happening? And if I went to a doctor would they even be able to do anything?

TIA x