Am I over-thinking things/being stupid?

[Rebecca]

To start with I have this guy (Lucan) I really like, and I know he likes me too because he's told me in the past (although we're not together).

When we first became friends there was another girl (Fern) who also became friends with us so we became known quickly as a trio and would have lot's of fun talking in a group. We had a group chat on Facebook and Lucan and Fern have always gotten along better together (in my opinion than me and Lucan) because they would find things funny that I didn't, and would share lot's of private jokes I wasn't in on... After a while I began to tire of the private jokes and voted to leave the group chat, things got better from then on as I was able to form a single relationship with Lucan rather than it being a 'trio'.

Me and Lucan talk all the time over text and are normally with each other at school. He knows everything about me (good and bad) and still claims to like me. He is my best friend and I would eventually like to get into a relationship with him again in the future (we've had a past relationship that we rushed too much and it went wrong).

Lately however I've found myself getting really jealous of Fern and Lucan's relationship and I feel as if he's been wanting to talk to her more than me. Because of this I feel as if they have something me and him will never have and I tend to find that our conversations aren't as full as they used to be (short answers).

I hate feeling like this , am I over-thinking their relationship?