It may be that both earlier experiences in your life and your hard breakup are informing your hesitancy. To move into a more intimate relationship may be anxiety-producing because you have loved and lost before. It tends to be that early relationships and experiences in childhood are linked in someway — not separate incidents. In any case it seems like your past is influencing what happens when you feel greater intimacy.
I’d recommend the Keeping the Love You Find by Harville Hendricks. This will give you some of the elements of how attachment theory works. I’d would then talk about how you might take action in changing this pattern with your therapist.