Here's the things that come to mind for me.
I would spend some time figuring out what specific parts of the experience didn't work. Like 2 weeks was too close together for him. Does he think once a month is more reasonable? does that work for you? or is it less about the actual time and about something else? Taking some time to really dissect can help get clarity for the future. It doesn't you'll never have an issues again.
I think there's an aspect of opening up that you really have to be in good shape with your partner and assume they have good intentions, and them about you.
In terms of the illness, it sounds like he might still be working through coming to terms with the changes it has caused in his life. That's something he needs to do work on for himself. This is especially true if it's a chronic condition.
Following that, it sounds like he might feel left out and like a part of the connection between the two of you is missing because of the changes to his health/life. Have you guys found a new way spent fun/exciting time together that he can do and is special for you? Having and activity or ritual or regular date night can really help with the reconnecting part that Galagirl talked about.
I assumed a lot from what you said, so if anything seems wrong my apologies and feel free to ignore.