Help me!

So I need some help on this. I have been dating this guy for almost 4 months and I have had a huge crush on him for over a year. A couple days ago he gave me his sweatshirt and I was excited about it. I do have a problem where I don’t like wearing other people’s clothes, but I thought that I wouldn’t care because it was his clothes and I love him and I’m comfortable with him. I have run into a problem though that when I tried to put it on for the first time, I couldn’t bring myself to put it on. I have always been a very anxious person, but I just thought it would be easy. All I had to do was put it on! But I am having trouble bringing myself to it. I need help! Why is this so hard for me?! What is wrong with me?!