. In short, your girlfriend should never know about your AAS usage.
Good luck.
Option 1: Just be super nice, it's only a couple of months. Tell her she is always right. Make her feel like a goddess. I have been doing this with my wife for 19 years bro, you can handle a couple months.
Option 2: Use your looks to meet a rich girl that you can live with for awhile. Take 20mg Cialis E3D, or EOD. Make love to her like never before, always go down before going to pound town. Lick her butt to test the waters and let her know you are down for anything. Make loud noises when banging to make her feel like she is the most awesomest sex partner.
Option 3: Hide your gear somewhere offsite where no one ventures. When you leave to retrieve your gear, switch multiple cars, do parkour and free running, and that should lose anyone who may be tailing you. If they do follow you to the stash spot, they are obviously on gear too, and you may need to spare a CC or two to keep them hush.
Option 3: Tell her you are in love with her and propose to her. Use a fake engagement ring. If she get the ring checked out and calls foul, act angry about getting ripped off and tell her you will fix it. When the lease is up, roll out but let her have the ring as a reminder of how savage you are. Worst case scenario is she says you assaulted her and you end up in prison for a couple years because you will for sure lose the case.... because you were selfish and only gave the person who followed you a CC of underdosed Tren Ace.
I have other options, hundreds actually, however some involve killing things with fire.