Sick and he wants more

So recently I've been really sick with a bad sinus infection and possibly turning into pneumonia. Yesterday my SO all day was wanting to have sex. We had sex 3 different time. 2 were 15 minutes apart. We normally have sex either every other day or every day. It just depends really. Since we've moved in together we've never had sex more than once in a day just because we both work and are exhausted. He hardly ever acts this way and I've been telling him I thought he lost interest in me so maybe that's why he is doing this.. idk? I'm super exhausted and it's hard to breathe so what should I do? I hate to be selfish and say no because I'm sick. Any tips?