Is there something I can do to change being moody all the time?
Sure! First of all, I am hearing that I think you would mesh well with flower essences. I don't know much about them, you should consult with someone that is knowledgeable/trained in them, but I really think they could help you. I also think there is a bit of a hormonal imbalance going on or actually it feels a bit like the thyroid and I'm hearing that sugar is your enemy. I will get off the sugar as much as possible.
Emotionally though, I feel that there are just irritations and resentments that are just bubbling under the surface. Things that have bugged you for a long time and they are like this constant irritation for you and that is the main cause of the moodiness. So I would encourage you to get to the bottom of those irritations. Basically allow them to come fully to the surface, deal with them and let them go. I beleive this is where the flower essences come in.
So take a look at it all, body, mind and spirit. The biggest thing is stop pushing these irritations down, they are growing into something bigger then they need to be. You are not doing anyone any favors by trying to ignore or squash them. You'll actually be better off dealing with them head on. It will be such a relief!