Let me see if I can clear this up for you.

Because THC is absorbed through the lining of the lungs, your blood pressure will naturally increase. This is your body's reaction to a sudden pollution of the lungs. It's a fight or flight response, it's adrenaline. Not only that, but the first time you smoke you get so worked up, your heart rate increases naturally. Sometimes so much it seems like you didn't even get high.

The reasons behind this don't really matter, but getting the "high" you expect isn't quite so easy to describe. You don't really "get" high, you just realize that you're already high. I don't really know how to explain this part.

Here's what I suggest doing.. Go into your bathroom, and smoke with the fan on and some incense (joss sticks) lit. Lock the door and sit down somewhere, so you won't get dizzy or get a "whitey" (drop in blood sugar due to adrenaline. Feels like you're gonna pass out or puke. If this happens, sit down and drink a soda. You'll be fine.) After you smoke, go sit down and listen to some music. (Jimi Hendrix or Cream are best, but whatever works for you.) Just try to observe the feelings you get, and enjoy the buzz. Your body will tingle, you'll think more creative and colorful things, and you'll just feel really good, sometimes almost giddy.

Just chill out and enjoy the effects, don't worry about getting caught.
If someone asks you (like you parents) why your eyes are red or you're scatterbrained, say you have a headache. You'll be fine.

Basically, just relax and enjoy the smoke, don't get too paranoid and remember you're smoking to enjoy it. Your heart rate will increase, but it goes back after a little while. You're not gonna have a heart attack. Nobody in the WRITTEN HISTORY OF TIME has died from smoking bud, so you don't really have anything to worry about.

And if you decide to not smoke again, you can send me whatever you have left, and I'll do some tests to make sure it's good bud. Purely scientific, of course.