Re: Cant breath
Sounds as if you had a bad anxiety attack after the day at the beach, perhaps got a little overheated on way home, the thoughts stuck with you, and by the time you smoked marijuana, had an anxiety attack.
Seems they have taken the right type blood work, cardio tests, etc. 80 bpm at home is not high, average is anywhere around 60-80 bpm. So when someone mentioned you had a high heartrate, it threw you into a panic mode. Sounds as if you are experiencing the medical term, tachycardia , which is rapid heartbeat. This is quite a common symptoms with anxiety/panic attacks, with the cant breathe feelings, dizziness, etc.
Marijuana seems to magnify alot of symptoms of anxiety, as does alcohol. If at all possible, try to kick the habit, also drinking sips of cold water when you experience the spells helps, avoid caffine as much as possible, any stimulants.
If after all this you are still experiencing episodes, consult your family doctor.