J.T.
I hope you're not offended, but I feel compelled to mention that when a man insists on sex even when it's inappropriate and unadvised such as immediately after a surgery or childbirth it is a strong indication of an abusive relationship. You didn't say anything else specific on this issue, but given that you have been divorced from him once, it seemed worth it to at least mention this for your consideration.
And no it's not unusual for a man to have a much more active libido, what is unusual is that he is not able to recognize that there are times when his needs do not come first and/or does and doesn't care and requires that he be serviced anyway. You NEVER have to give in (sometimes it may be advisable to give it a go even if you're not into it b/c you had a long day at work). When it's a health issue though, you need to look out for your own interests, even when he won't. You need to sit down and have a serious talk with your husband, discuss other possibilities of ways that you can be intimate that may be less stressful (and more appropriate) for you physically, set out a schedule for intercourse if need be to ensure that it is not such a taxing daily occurrence. You don't want to lose the intimacy that comes from a good sex life with your husband , but feeling obligated and forced into sex will only create resentment and divide you. You didn't mention whether or not you enjoy this obligatory sex, but I know I would have a hard time with it under the circumstances you described. Setting some limits and exploring other options for intimacy may help you both to get more out of your sex lives and relieve some of the burden (physical and emotional) that you both seem to carry about the issue.
Best of luck.