Fiance' just doesnt understand

I'm 18 wks pregnant and I have some days where I absolutely don't want to be touched by anyone even my fiance'. We are usually very affectionate,always kissing,touching,ect. But since being pregnant I have my days. He gets upset by this and I've tried explaining to him that it's just the hormones, it won't be like this forever, it's nothing he's done and I profusely apologize over and over. He brings it up often that I don't want him to touch me and it makes me feel bad and a little upset that he doesn't or won't understand. Is there anything else I can do bc its literally becoming an everyday issue. I know he probably doesn't do it to upset me since he seems very upset/sad that I don't want to be touched but I don't know how else to get my feelings across!