Should I be worried???

Hi everyone!

Looking for some advise, my boyfriend and I have been together for about two years and have never had any kind of huge fights or distrust in our relationship.

There was an instance a few months ago where my boyfriend mentioned he had been talking to an ex for a few weeks but she stopped replying to him after he mentioned he had a new girlfriend. I was super upset for a moment but kind of thought nothing of it and my boyfriend made anniversary posts so I assumed it was dealt with since now we are publicly dating.

However, last Saturday my boyfriend posted on his Instagram story and I grabbed his phone to change the song in the car and a girl, he has never mentioned before, had replied to his story with a bunch of hearts. I didn’t say anything but since then it’s all I can think about. Her Instagram is private and I have no idea who she is! And being the person I am I spent some time looking through who my boyfriend is following on Instagram and he follows about 25% brands, 5% family and friends and 70% random local girls.

I’m assuming these are all girls he had previously matched with on tinder (he admitted to using tinder to hook up a lot before we met). And it’s all I’ve been able to think about. I’m very open with my phone and let him use it whenever and never hide it, but he will never leave his phone unattended with me (even when going to the bathroom) and doesn’t let me see messages. Should I be concerned??? What do I do???