There's no right or wrong answer to your question; because the response isn't a one size fits all.

This is just what I personally did.

I would say it was just before the 2 month mark in my relationship with my bf where I realised things could get quite serious (relationship wise) that I told him I'm bipolar. I didn't want him to make a judgement on me beforehand when he could get to know me a little bit; and I didn't want to tell him at the last hour either.

Sounds like you need a little more than "like" at this stage to spill the beans. I'd wait a little while and see if anything develops from your relationship.