Why do I have laughing problems?

Most of the time when looking at other people face to face just me and them, I either smile or laugh for no reason and can't stop. I can't stop because it feels involuntary even though it's not. When I try to stop, it's just so hard. And people stare at me, or if I know them they're like what is so funny or why are you laughing? And I tell them nothing but keep smiling or laughing and it's embarring. Actually when I laugh, I don't laugh out loud. I smile hard and laugh silently making no noise or sound. But my body moves up and down, of course. Also, whenever there is a reason to laugh, I keep laughing at it because it is just so funny and I also still can't stop. But other normal people who are around me laugh once and then stop, get over it, and move on. But not me. I can't get the funny thing out of my head and I keep laughing at it. Then eventually I stop but it comes back later and lasts like that for days until it finally goes away and I don't think it's funny anymore. This is also embarring. Also, when I get in trouble, I laugh. I know there's nothing funny about it at all because it is serious and I should not have done what I did or I learned my lesson, but I still laugh and can't help it. Then I get into even more trouble and I stop laughing. But then I laugh again. That's not embarring, but it's painful and torturing. What is wrong with me? I have four questions. The first three should all have the same answer to all three questions, not three different answers. One: Why do I smile or laugh for no reason and have a hard time to stop and keep a straight face when looking at someone? Two: Why can I not stop laughing when I hear something funny? Three: Why can't I control my laughter when I get in trouble but know that it's serious? Is this all a disorder? If so, what is it called? If not, then just why am I doing this and find it hard to stop? Four: How can I stop this from happening?