Is it normal to enjoy sex with someone you hate?

I did something very stupid and illegal 5 months ago. Unfortunately I was caught and since then I'm being threatened with police action and public humiliation... truth is if my husband found out I'd be in deep trouble and could lose my family.

I feel so trapped, this man who I work for and see once a week makes me touch him, perform oral sex on him and he touches me too. He's never forced me to have full penetrative sex with him, but he does force his fingers inside me and makes me kneel on the floor... you can guess the rest. Sometimes he is rough and says mean things to me, not caring if I cry or say "no". If I don't submit to his demands, then he will spill the beans.... I will lose my job, my family and probably have a police record. Yes I know I am very stupid and I shouldn't have got myself in this mess, but no one is perfect. The last time we were together I decided to just let him do what he wanted without tears, complaints or tantrums. But a weird thing happened I had an orgasm and now I feel ashamed. He laughed his head off and taunted me. I feel so ashamed. I have such low regard for this man and for myself. Is it normal that i had an orgasm when I clearly hate this man?