Squeaking wheel on every rotation - please help

[JChase]

Hello all, i've got some problems with (what i think) is my drivers side rear wheel, and couldnt find a closely similar problem on here so any advice would be welcome.

For some time now ive had a squeaking nose coming from my rear wheel constantly when i drive. i will try to describe it as best i can even if it sounds weird. if you can imagine each rotation makes a squeak so the slower it is its like -squeaaaaaak - squeaaaaak - as it turns and if im driving fast you can still hear it, but its like double time squeak-squeak-squeak very fast. It has no relation to breaking whatsoever, but its now added a new sound which has a high pierced shreik when i do brake, which happenes aswell as the rotation squeak and carries on with the regular squeak after ive braked. I took it to my regular mechanic a few days ago, they just said it was dirty and needed cleaning and it happened cos i dont use it too often (i use the car a few times a week) but even im intelligent enough to know that if its just a problem of standing still too long then the noise would get lesser the more i drove it, but actually the opposite is true - the noise gets louder the longer i drive the car and the other day i could actually hear it over the cd player. After they cleaned it, it lessened the noise for a short while but then it came back again so its clearly not what they said.
I want to take it to another garage where they will properly take the wheel entirely off and check the brake pad and disc for a stone or whatever that might be caught or a loose wheel bearing which ive heard can happen and not just clean it, cos i dont want to keep driving it if its doing damage.

If anyone has had a similar problem or knows what it might be please let me know cos i dont want the next garage searching for everything under the sun and rip me off when it may be something quite simple that i dont know about.

Thank you!