Hi there, sorry you are having a tough go of it. Some more information would be helpful!

Could you answer these questions?

Are your bunnies spayed/neutered?
If so, for how long (for each)?
If not, why not?

Please describe your bunnies’ current housing set-up (living together, as neighbors, etc.).

Did you allow the bunnies to “settle-in”?
How would you describe your bunnies reactions towards each other (answer for each bunny): shy, scared, curious, calm, aggressive, excited, affectionate, etc.?
Have you done any “pre-bonding” (cage or litter box swaps, etc.)?
If so, for how long?
Have you started sessions yet?
How long have you been working on bonding your bunnies?
How frequently do you have bonding sessions, and how long are they?
Have you tried any stressing techniques?

Ok that is helpful. It hasn’t been very long at all, so please try to be patient. Bonding can take several weeks in easy cases to several months in hard cases.

So first of all you should give your new rabbit a lot more time to settle in before starting bonding, especially because he is shy. If you start off with a very fearful rabbit it makes it harder for a strong bond to form.

I also recommend that for now you set up side-by-side pens so the rabbits are neighbors. Be extra sure they can’t nip each other through the fencing (so either make a 4-6 inch gap or use small mesh wire between them). Your free-roam rabbit will not be happy about this at first, but it will help with the bonding. Once your new bun seems more relaxed (I would give it 1-2 weeks minimum), start swapping which bun is in which pen every day or two. If it’s not possible to have side by side pens, then swap which bun is penned and which one is free-roamed. Don’t clean the litter boxes right before the swap, you want the buns to get very used to each other’s scent. Continue this for at least a couple of weeks, depending on the bun’s behavior. You want to wait until they seem really relaxed towards each other, even right after the swaps. Feed them their salads and pellets on opposite sides of the fence but near each other to start building some positive associations. You might see them start to mirror behavior, this is great.

Right now your current bun is just viewing the new bun as an “intruder” to her territory, so the goal with this pre-bonding phase is to have her lose track of her territory a bit and see the new bun as less of a threat.

AFTER all of that, pick a very neutral location, ideally somewhere out of smelling range. Since the fought in the bathroom you might want to try somewhere else. When you put them together it’s very important to prevent fighting, so don’t be afraid to have your hands on them a lot at first. Do lots of petting and scent swapping, and keep sessions super short at first. Do super short sessions daily (while continuing the pen swaps) until they start to seem a bit more relaxed, then start increasing the length of sessions gradually.

I’ll stop there for now because I think that’s enough to get you started! Feel free to post  updates and keep asking questions.