How can I stop my 2 year old being naughty at bedtime?

My daughter used to be great at bedtime but all of a sudden she has started to play up. As soon as i say its bedtime she starts to get upset and says she doesn't want to go to bed, after enough coaxing i can get her up to her room but then its another battle to get her into her bed. Ive started to stroke her face to relax her once shes in bed which worked a few times but now shes decided to throw another tantrum as soon as i say goodnight and leave the room and she demands i stroke her face for longer. I refuse as i don't want her to get her own way but last night i ended up having to leave her to cry which i hate doing. Eventually she dropped off to sleep but now tonight shes got even worse. We had the usual dramas as usual but this time after eventually getting her to relax she now keeps getting out of bed and coming to me and then crying hysterically when i return her to her bed. Ive tried being firm and not losing my temper but she just seems to be getting gradually worse every night. Has anyone else been through anything similar and was it just a phase? Im panicking as im 5 months pregnant and have never had this issue before, i certainly don't want it to continue once the new baby has arrived.