Hardest break-up so far, does bipolar affect this?

I am simply confused why this one is the hardest, and the title I wanted was too long: Hardest break-up but shortest relationship so far. Bipolar related?

My first relationship lasted for 9 months, after the break up I experienced my first hypomanic episode, which during I got into a new relationship (after knowing the guy for 4 days). Basically I was super happy after breaking up, even tho our relationship was good overall.

The second relationship lasted for 2 years and 2 months. It wasn't a great one, and after breaking up I experienced my second hypomanic episode. I thought I was simply happy about it ending, which I sure was, but the happiness just escalated.

This time, the relationship barely started. We hung out as fwb or like just two people who liked each other. For just 4 weeks, but almost every day. Spent nights over, went shopping together, he was the first man to get me flowers, too. I was very open about my mental issues from the start, he didn't mind. I became his girlfriend one day, and just 4 days later he said he isn't ready for a relationship and doesn't want to see me.

I was crushed. That night I cried, just cried. The next whole day I cried from waking up to going to bed again, couldn't eat. I had zero appetite. The day after that (yesterday) couldn't cry anymore but kept thinking about him and what could have been different.

Today, I am starting new meds, hoping they will make this a bit easier. I'm just confused how such a short relationship, barely one, hurt so much more than ending the previous longer ones? And this time, I didn't start a hypomanic episode but a depressive one instead.

Also, if anyone has any tips on surviving through a break-up and a depressive episode at once, please do tell.