How do i tell my husband that i need some space without him freaking out?

i'm used to having some alone time to read, do hobbies, daydream, whatever. but i haven't had ANY since my husband moved in (just before we got married). I don't even get solitary bathroom time for showering & grooming (only for toilet related things--and even then he gets cranky when i take too long. yes i do occionally linger, because it's the only time i get to myself!!) the thing is, we're starting to bicker, constantly. i love him a lot, i really do, but i'm feeling confined and imposed on a lot lately. he makes me tense & edgey & i've been defensive & snappy a lot (so has he). i feel like he's always criticizing me, he questions everything i do, even things like why do i sit to shave my legs when i get the chance, instead of doing it in the shower (which i have only had 2 by myself in over a year). he acts like he thinks i'm going to cheat on him any minute (or that i already have & that i hide it from him). i'm not going to, and i tell him that, he doesn't really believe me.