Well, could have been much worse, than texting. I can appreciate, his being hurt by this. Need to answer, to yourself, why, a friendship, with your ex, was an important part of your life. What needs were being met there? That weren't being met, by your bf?

Not 'quite' cheating, per se; but it's certainly bordering on a fine line, of trust, in your relationship. Plus, took discovery, to find out about this friendship. As in, there was a certain lack of honesty.

Moving forward, will take more than words and apologies. Some reconnecting, with one another, could help. How about relationship counseling?