It feels like it almost is going to become a charley horse but never does..??

Could it be a blood clot forming?

I didn't hurt the leg or muscle at all and it has been feeling this way for 4 or 5 days now.
I've been taking aspirin just in case to thin the blood.

Just wondering if anyone has had a blood clot and what it feels like, is it an instant thing or does it build up?

thanks for any help on this.