Welcome to the boards, heliosun.
Let's start with the simpler part: here are three pieces that can fill you in on lesbian safer sex. The first is a piece about barriers that's just about what barriers to use for what activities, regardless of your gender or that of your partners. The second is another inclusive guide about all aspects of safer sex, including testing. The last is a specific piece from someone who worked this out for herself.
• All the Barriers! All the Time!
• Safe, Sound & Sexy: A Safer Sex How-To
• Figuring Out How to Be a Lesbian Safer Sexpert
I'm so sorry that you experienced abuse. It's certainly valid to feel afraid of being in an unhealthy relationship again, especially when you've been in one to know how it can feel and all the impacts it can have. They are also sometimes much harder to get out of. These are all valid and understandable fears. I've been here a bunch of times myself: I get it.
In terms of how to get past these fears, around sex or anything else, with your current girlfriend, can you tell me a little about the relationship so far? How have you felt in it? has it felt healthy and equitable? Have you built a good deal of trust with her? Have you talked with her about your previous abuse? Does anything about this relationship, so far, give you any concerns -- not based on your last relationship and its impacts, but just based on this one?