I might be characterless

Got into a relationship 2 months ago, this is my 3rd relationship. I'm seeing the same pattern again with myself Enjoy each other's company -> find her attractive -> one of us asks for a relationship -> we get into a relationship -> few months later I feel 'bored', I feel she's not attractive -> breakup for something random and I don't even feel bad for a few days, start feeling bad after a week to the extent of drinking and crying every night for a few weeks.

With this girl I'm with, earlier I felt she's the most attractive girl I've been with, now all of a sudden I don't even feel much of an attraction towards her. I get jealous seeing other couples despite being in a relationship. Now she's clearly into me more than I am. We've had sex 4 times already and we both enjoyed it always.

I don't want to do this (breakup) again, she's a really sweet girl. But at the same time I don't want to be with someone I'm not longer attracted to.

Am I characterless? I think so. Idk what to do to change this behaviour, therapy? Talk with my partner? Friends? Help a brother out