You don’t have to dress up in fancy underwear!
DP and I have been together 9 years and there’s still a spark. I put that down to the fact that we don’t live together, so still have to make an effort to spend time together. Once you’re always there, it’s easy for you both to stop seeing each other as someone you have to impress, you just become part of the furniture.
Your medical issues can’t be helping. You must feel like crap a lot of the time and the fact that it’s inhibiting your sex life must be a big part of the spark going from your relationship. You must keep pushing to get this sorted out, it’s having a massive impact on your life. Maybe get him to come along to your next appointment and tell them it’s fucking with his sex life - sadly that’s probably the only way it will be dealt with 
However, in the meantime there are other things you could do - we don’t do PIV most of the time anyway due to contraceptive issues, so could you prioritise other types of intimacy? Long kisses, feeling each other up, hand stuff etc - it’s vital to have that connection if you want to stop being flatmates but I understand why you don’t feel like it.
What helps for us (and we go through less amorous spells when these things are missing) :
Six second kiss when he comes in the door or leaves. Not just a granny peck on the cheek, a proper kiss.
Holding hands, touching thighs, arms around each other etc when watching TV
He gives me a foot rub and I give him a back tickle. Every night we spend together (3 times a week)
We send messages saying “thinking of you” or Love You during the day. He’s a bit crap at this sometimes but I’ve made the point that it’s important to me to hear from him when we’re not together, otherwise he can go until 11pm before I hear anything and I feel forgotten, which makes me close down emotionally.
We tell each other often (face to face) that we love each other or that he thinks I’m beautiful or that he makes me melt when he looks at me a certain way. I don’t do flirting, never have, but I’ll put on a tight vest top with my PJ trousers because I know he’ll like it, and then he gets the signal that I’m in the mood.
We don’t go out often as both have our kids around much of the time, but we make time for lunch about once a week, and prioritise our time together when we’re both free. We try to schedule other things for the days we’re not together, so we don’t spend much time with each other’s families, but that means when we are together it’s more about us, rather than fitting in with hobbies and visiting family etc.
We also assume we’ll be having sex and operate an ‘opt-out’ system rather than ‘opt-in’, so we go to bed assuming we will be doing something. That may be one sided or less than the whole hog, but it means we keep the connection going. But that’s one for layer when you’ve got your Gynae issues sorted. That has to be your priority. If need be make a complaint as it sounds like you’re being fobbed off.