彼は、だまされてばかりいて、疑心暗鬼になっている。

he; him; his; boyfriend

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

to trick; to cheat; to deceive; to coax; to wheedle; to soothe and humor (humour)

only; merely; nothing but; no more than; approximately; about; just (finished, etc.); as if to; (as though) about to; indicates emphasis; always; constantly

Suspicion will raise bogies; Once you suspect something, everything else will look suspicious; Jumping at shadows

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to become; to get; to grow; to be; to reach; to attain; to result in; to prove to be; to consist of; to be composed of; to succeed; to be complete; to change into; to be exchanged for; to play a role; to be promoted; to do ...