pre engagement/wedding jitters

I already have generalized anxiety disorder and depression and now I'm going through the biggest change in my life. My boyfriend and I have been together for 3 years and its been amazing! He is the best thing in my life and in so excited to spend my life with him but lately I've been having thoughts that sound like: "you can do better. you,don't really love him. are you sure you want to marry him? you should just break up." also I'm finding myself being bothered by all the little things I don't like about him. they only slightly irritated me before now its driving me crazy. I know he is proposing soon also he is my longest relationship and I have only really been in the lovey dovey butterfly stage of a relationships. when those butterflies went away this time I started freaking out thinking I don't love him anymore because that's all I knew...now I know love is a choice not just a feeling and those butterflies come and go. but my anxiety loves to take those pre wedding thoughts and changes in our relationship and not let go. I've read thst feeling this way is normal because getting married is a huge decision...i just like to hear if other ladies went through it and howthey got through it. so please share your stories. I hate these feelings and these thoughts because I love him so much and want to be his wife. I hate this!