Help!!

Okay so I'm a ftm due in July & im dyin for a smoke I quit before I got Prego & I made it all the way to my 2nd trimester but now im so stressed out constantly worrying about if my relationship will survive if I'll be able to be a good mom & all of its got me dyin to smoke a cigarette. & I don't know what to do. On days where I don't have to work or go out of the house I lock myself in my room to prevent me from buying them or bummin 1 from someone. Ugh😩 what to do?