Definitely gas bubbles. You can tell because they are smooth, etc. If they were just mechanical openings due to a light press not fusing the curds, they would look more rough and jagged. If it was bad stuff, it would smell foul, and rotten, etc. The bitterness could be due to excess culture or rennet. Sometimes this will fade if you age it out longer. Cheese goes through weird phases, and sometimes it can be good quite young, then it goes all unsatisfying on you for awhile, then it gets good again as it ages out more. So, you might want to keep some of it to age another couple months and then revisit it and see how it develops.
Anyway, given that you've eaten some, and not become ill, you're good to share it with others.