What would you suggest to do about jealousy?

I am naturally a jealous person, and I hate it. Well, when someone screws me over it makes it 10x worse. My gf is a flirt, see where this could be bad? Whenever someone comes up to her and hits on her, she kinda does this smile flirty thing back... it's a look I wish she'd get rid of. But most importantly she totally forgets about me, like doesn't even introduce me. Which gets me heated. I can feel my blood pressure rising. It literally feels like my heart is going to explode. Well, now little things get to me like when she was on the phone yesterday she told her friends she was staying in, laying low, tired bc SHE spent time with family, etc.. didn't say a word about me being there, or laying low with her, or anything. It's ridiculous. She left me for someone else when we were engaged a yr ago, so I am struggling, and trying to rebuild something almost impossible to rebuild, but I get jealous and my feelings get hurt, and I get in this funk, and sometimes I yell and cuss at her when she does things like invites some tramp that sends her naked pics to her bday party and tries to hide it from me so I don't get mad.. it's disrespectful. She isnt friends with her now, but it's the point. It's my reaction, it's like I almost can't calm myself down. I want to be able to control it. I am 25, she is 33.. I want to be able to be civil and not scream. Any advice? It's an awful feeling. Any advice on controlling jeaously at all?