Clen can fuck you up and has the potential to kill. All the more if combined with T3 or other stimulants. Death would probably be heart failure. You probably found that heart pounding very frightening.
Give your body a rest. Don't touch that shit for at least a week.
Is the product a solution or suspension? I can't remember. If a suspension, one could draw up a high amount from the bottom of the bottle if not well shaken. If a suspension, that is a route to overdosing during bottling.
As you have seen, it has a long half life and when you get in trouble, its a long term house of pain.
If someone took a dose every day, blood levels would build for a while. So watch that too.
Probably best to take baby steps with this stuff. All the more with a different source or lot/batch.
Taking insulin also has the potential to kill.