Before I begin, please PLEASE go gentle on me. I do not have much self confidence at the moment and can't take a beating 
There is a woman I know, let's call her Lorna, an acquaintance/friend who is everything I want to be. She's pretty, funny, confident, outgoing, good at the sport we do (which is how we met), clever blah blah. She's also a lovely person and has been nothing but nice to me.
My OH runs his own business which is linked to the mutual sport. She is unemployed at the moment, so he has taken her on to do odd bits and bats and she often attends trade fairs with him etc. For some reason, I feel wildly jealous about it, and it's making me feel all sorts of horrible things towards her (which of course I keep to myself).
Part of the problem is that I have always helped OH with his business. I enjoy it, personally think I am quite good at it and he has always said that when he can afford it he'd take me on. Now I feel like she is getting asked to do everything and is better than me and it just confirms my own feelings of uselessness. I feel like I am rubbish at everything, unsociable, boring, and that Lorna is the total opposite. It just confirms my own feelings of inadequacy.
I feel a bit...hurt and feel angry towards Lorna, although I know this is totally irrational.
It's eating me up inside and I am avoiding events that she is at because I feel so upset about it all.
Having written that, I can see just how unreasonable i am being. But right now I feel so crap about my life this just isn't helping. Why do I feel like a stupid fucking jealous child? I'm in my 30s FGS.