Partner seems protective of son-any advice?

[GenuineDad123]

Hi,
My partner of eight months has a young boy-toddler. She was keen for me to meet him initially. I've met him a few times now, he's a very polite well mannered boy. However, my partner now seems to have created a barrier between me and her son. She has on a few occasions got angry about things i've said/done when we've all met.
Its put me off to be honest. It seems like she is trying to protect her son from the truth, things that he will find out over time anyway. This includes things like her not liking me showing her son photos of my daughter. She has always spoke very highly of her son (understand that-i have seven year old daughter). Sometimes its felt like I have a lot to live up to. It sometimes feels like she is waiting for her son to accept me then we can move the relationship further, and that she holds her son in high esteem. Before we met, my partner, her son and her ex had all been on holiday together. I found this difficult to understand (but accepted it was before we met). The ex used to put the son to bed in her house. They still share/part own material items like car/house/phone service, and generally there appeared to be confusing boundaries.
So my main concern is that her son won't accept me as he might still think the father is with his mum, that the way his mum has acted when weve met has given the son the wrong impression of me, and that she won't fully allow me to interact/be myself with her son without her stepping in, and, that she hasn't moved on and got over her ex.
Any advice appreciated.