How to not aways be anxious about my relationship?

I am ALWAYS anxious!! My boyfriend and I have been through a lot together. We have known eachother and been good friends for years and finally started dating 2 years ago. Through out our relationship a lot of stuff has happened....lots of ups and downs but within the past 3-4 months he finally got a job and things are SO much better. However I always find myself being so anxious about my relationship. my boyfriend since he has recently found a job....is now always soooo busy so he cant be around a lot or isnt able to talk a lot either. I dont know why but I question everything! I wonder if he really loves me....if he wants to be with me,.... if hes serious about our relationship.... if im good enough for him.....the list goes on and on. Yes, I have talked to him about how I feel thousands of times and he always reassures me that YES he loves me YES he wants to be with me YES he's serious about our relationship. I ask him if he ever worries about our relationship and he says no....he never does! He never feels the need to be concrned....he says he's never thought about breaking up with me or anything. I LOVE him so much!! and want to be with him. I have realized that this is my issue....not his. He does all he can by reassuring me but its my choice to still continue to worry. I always analyze everything! from the way he says I love you to the way his texts are worded. I feel like if hes in a bad mood its my fault and our relationship could be over or any tiny thing that isnt perfect will lead to a huge issue and break us up. ITS EXHAUSTING! I analyze what time I should text him in the morning or should I just let him text me? Im so tired of being this way because he isnt this way AT ALL. my boyfriend is very go with the flow. I find myself only being at peace when hes around. Whenever he isnt around it stresses me out and my blood pressure is through the roof again! Im fine when he is around....I just need to learn to not be so obsessive and worry and analyze everything when he isnt around because its very tiresome. I need advice of how to be chill when he isnt around. what state of mind should I be in? how to not be obsessive when it comes time to text or call him. I know I sound crazy but I just want to fix this and be able to go on with my life and relationship without stressing about every tiny detail all the time!