I hope you got some sleep OP.
wasnt scared at any point , just wanted to avoid social awkwardness by complying
This has affected so many of us. As women we are socialised to make people happy, in the UK our whole communication culture is to evade and ‘be polite’ rather than calmly be clear about our boundaries.
His marriage / fidelity isn’t your responsibility so don’t feel guilty. But you have made a good and string choice not to sleep with married men on your own terms. Because men who cheat are sleazes, and because they are not available and you have a right to choose not to be a shag.
His fidelity was his responsibility, and respecting your boundaries was his responsibility and he failed.
Men like this do not deserve our delicacy around social awkwardness.
Do not turn this on yourself and blame yourself OP, but what you could take from this for the future is that we do not have to explain ‘no’.
There is no argument against it.
It doesn’t have to be ‘because I don’t sleep with married men’ or ‘because I have my period’ . “No. I do not want to and I do not feel comfort with this. Stop now” said firmly and decisively, not pleadingly.
It takes practice because we are not brought up with these communication skills. Say it out loud now, and again tomorrow. And move forward, don’t look back.
I hope talking with your friend helps you.
Have a good day - this vile creep doesn’t deserve to spoil any more of your time.