Anxiety tips please!

I have some bad anxiety and it’s fairly new to me. Over the years it’s gotten worse. Well with my bf sometimes i get paranoid and anxious that he’s cheating on me or doing something he shouldn’t be when i work my late shifts like tonight. He has never done anything like cheated or done anything for me to believe he’s doing something wrong. I have been cheated on in all my other relationships so my anxiety stems from that. I know he isn’t them but sometimes the overwhelming feeling is to much and i let it win and blow up his phone and have an anxiety attack. It’s starting to become an issue with him because he feels I don’t trust him and I realize it comes off that way but I do. I was just wondering what were some things I could do to help the anxiety subside or calm down when i feel as anxious as i do when those situations arise.