She just wont do it

My 4 year old is so scared of sleeping by her self i just dont know what to do she has her room and she just starts crying hysterically when im about to leave her room . I've tried laying with her reading her books and when sometimes she has fallen asleep i come to my room and like 2 hours later she comes next to me telling me she doesnt want to be alone this happens 2 to 3 times every night i have to keep walking her back to her bed and wait till she falls asleep im tired plus im pregnant and im trying to make her feel safe and pray and leave her lights on but nope 😔 i feel so bad when she cries like that ive also tried being the though mom but honesty it breaks my heart