Relationship question?

i have been with my gf for 3 yrs now and she lives with me and she wants a set of keys now to my flat, we have had ups & downs we have argued & cat fights in the relationship. I get nervous she is going to leave me all the time, this happens all the time what sort of help his out there for this problem because i hate feeling like this i get scared & nervous i shake & get upset quite bad how and what can i do to deal with this cus i aint felt like this before i think i need mediac or psycological help or something but dont know where to go for help or get help from anyone can help me also i do have anxiety issues to with sme depression