whats wrong with me

so me and my bf were having sex the other day he was totally into it he went down on me i went down on him we did it doggy style and cowgirl style then missionary style then back to cowgirl idk what was wrong with me i mean im the one that suggested we have sex but for some reason when we started i just got umm like depressed i guess i had to keep faking like i was enjoying it because i didnt want to worry him every time he would look at me i would fake a moan or fake a smile bit me lip like i was so turned on but i think he noticed because every other time we are about to do it im well "super wet" down there but this time i wasnt then after a while he finally asked if i was alright he said i had a sad look on my face and i was like im fine im probably just tired then i said maybe we should stop and he was like those are words a guy never wants to here we awkwardly laughed a little .....idk why i felt that way. does anyone else get that way? whats wrong with me?