Situational Erections

Hello all, I’ve been experiencing occasional ED with my new fling. Sometimes I have no problem getting it up, others it just doesn’t want to go. In most cases I’ll get aroused during four play and take care of her but when she goes to return the favor I just can’t get it up anymore. I feel like I’m in my own head leading me to believe it’s highly psychological. My heart rate is sky high and I feel very anxious about it. Just started the program and saw box breathing as a good start. Does any of you have a similar issue or remedies/solutions in the moment to help?