temper tantrums

My son is 7 years old almost 8 (July 26), and he does have ADHD. He is a really great kid and does not have any behavioral problems, except for when it comes time to do what he is told. Basically what I mean by that, is that it seems like whenever we allow him to do something that he really enjoys, and we tell him ok, it's time to leave, he throws a huge tantrum and starts crying.
For example:
My husband took him to the skatepark with one of his friends, so they could ride their skateboards, and when it came time to leave, he threw a huge fit and basically threw himself on the ground crying and screaming. My husband had to literally pick him up off the ground and carry him to the truck. Once they got inside the truck, the whole way home, my son kept saying really horrible things to my husband, like, he wished that something bad would happen to him (calling him by his first name the whole time), and that he wished somebody would hurt him and so on!
I just don't understand where all of that anger comes from when he is upset like that, because when he's angry he just says some really hurtful things sometimes to the both of us. He's been the only child for all of these years, but now I am pregnant with our second one and he is very excited. I just keep trying to tell him that once the baby comes, that things are really gonna be different and that it's not gonna be everything just for him anymore. He is very sweet, thoughtful, and loving and has always been that way, but it's just that whenever he doesn't get his way, he throws these tantrums.
Please try to help me figure this out, because we are very concerned and we just want to know what might me going on with him, if it's a phase or not!

Thank you
Stacie

[RockRose]

Stacie,  your post is kind of weird to read.  Quote:

" He is a really great kid and does not have any behavioral problems, except for when it comes time to do what he is told. "

Is your husband his father?

[stacie34]

Sent by stacie34 less than a minute ago
Sorry for the confusion about my post. Let me explain it again. First of all my husband is his father, I guess I made that part sound a little confusing. Also, my son is ADHD and he is a wonderful child. We do not have any problems with him except for when it comes time to really doing something that he's told, and it's mostly when we take him somewhere that he really wants to be. That is the only issue that we are having, because we tell him before we even take him to these fun places, that when it's time to go do not give us a hard time.
But, of course once it's time to leave, he gets really upset. My only question for basically writing this post is because I just want to know if this is a normal thing that a 7 year old boy should be doing, or is it just a phase. Like I said before and I will emphazize again, he is a wonderful child! He's very loving, thoughtful, caring, bright and does very well in school with everything. It's just this one thing that we are having problems with!