Feeling physically uncomfortable at Partner's House

Last summer my Meta moved in with our hinge and they now have a 3 month old together. I have been dating my partner for over 3 years, and they have been dating just over 2 years. I used to go to his place fairly often but he still mostly came to mine bc of my kids. I've been trying to go over to their place more often so that he isn't skipping his evening baby duty and she can get a break (especially since he is back at work). However, the last 2 to 3 times I've been there I have been on edge and physically uncomfortable the entire time. I don't know where anything is and have to ask her. My offers to help with the baby are rejected. Last night I just gave up and went to sleep at 9pm as the baby was taking a long time to settle and I was just alone in the bedroom the whole time. I guess I don't really know what to do or say or what I should expect. I don't know WHY I'm on edge or in physical discomfort the entire time and I hate feeling like this.

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