Danger Will Robinson!
Granted clen isn't exactly like ephedrine, but if you don't even know your BF at this point, you should really go get a full physical. Blood work etc... Make sure you don't have any surprises, and also make sure you are already eating clean, because otherwise the second you stop the clen it will come back on twice as fast.
But otherwise, clen isn't something to 'play' with and should be monitored and used with extreme caution. I've known people who have put themselves in the hospital after a week of playing with the stuff because they were severely over weight and their bodies just couldn't handle the shock / release of cholesterols and toxins into their system in such short order.
If you have high BP or high cholesterol already, clen is a BAD idea. Just IMO FYI.