Relationship overthinking

Hi so I think I self sabotage my relationships like I tend to end them fairly quickly but rightly so because I know they aren’t for me and I feel like it’s happening again only this time I’m really in love with the guy but I’m just constantly overthinking. Like I know he’s loyal and he’s so caring and polite towards me but there’s always something I focus on to overthink and my only conclusion to solve it is to break up. Idk why I just jump to breaking up because that’s really not what I want to do but that’s just how my brain works:( I guess I’m just not used to long term relationships and am always on my toes for when it’ll end when I shouldnt think like that and I want to overcome this. Truthfully my bf is a great guy and I feel terrible for nitpicking certain stuff(of course I don’t say it) and just looking for reasons to end it when I don’t want to and know I will be miserable if I did. I just feel like I let my insecurities get in the way of my happiness. I’m sure some of you will recommend therapy but I’ve already done that in the past and it didn’t help much and right now I’m not in the financial position to be in it again. I just want advice from someone who can relate or who has suggestions for what I can do for myself🥺💗