Hi Claudia,
Sorry about your issues. I hope your condition will soon improve. I didn't have any swelling at all (bilateral Dr. Gross patient back in December 2016), so I can't be of much help there. It does appear to be late in the game to have swelling 3 months after surgery though. I hope Dr. Gross's staff will have an answer for you.
I'm replying to help assuage any concerns about device "slippage"/loosening et. al. I'm not an expert of course, but I was kind of paranoid about device issues, and had a few questions to ask the staff about the likelihood of those unfortunate issues occurring. I was relieved to hear that device failure is extremely rare (for Dr. Gross), and it would take the equivalent force of jumping off a 1-2 story roof to get a cup/cap to "slip".
This advice made me feel much less worried. I hope it will ease your concerns as well. You have less bone density, and that is why you've been put on the "slow" program. Again, not being a physician, I am still of the understanding that this doesn't place you in any additional risk categories for device failure than the rest of us. I think your density levels only increase the chance of a femoral fracture during the initial months post-surgery.
I hope your condition improves (hopefully the swelling is related to more activity, and nothing else).
Good luck