I’m scared of being in a relationship...how do I move on

Hey guys, so I’m 18 years old and I’m in college, I have had plenty of opportunities to date,and have had plenty crushes as well. Ok not plenty, maybe like two. But the problem is that I’m perfectly alright have a one sided crush, and I know that sounds stupid but hear me out. I had a bad experience with a boy as a child and ever since it’s really hard for me to emotionally connect with guys. I’m fine liking them, but the second they reciprocate the feelings back, I’m out. It’s like I’m so scared and I just literally freeze. I get nauseous, dizzy, and I feel like I’m going to pass out. And people have told me, “oh you just really like the guy, you’re just feeling butterflies” but trust me I know that’s not butterflies. For example, I was hanging out with a friend last weekend and I met her friend, and he was starting to make a move on me (he even told my friend when I left the room to use the bathroom and she told me). After that, every time his leg brushed mine, I felt so sick and nauseous. It was so nerve wracking. But he’s a sweet guy, cue, and I wouldn’t mind getting to know him. But the second he (or any guys ever) stars liking me I freak out. I get so scared, and I don’t even know of what. Also my mom has engrained it into my memory that sex before marriage is absolutely disgraceful, but the thing is I’ve already had sex (she doesn’t know obviously). It’s strange, I’m perfectly alright having sex, but the second emotions come into the equation I become terrified. I’m tired of this, I really want to move on.

What do you guys think? Any ideas or helpful tips?