7 month old thats waking at same time each night?

Can anyone help, my son is nearly 8 months old and for the past 3 weeks he has woken at the same time each night, 11pm, sometimes 1am then 4am, he has 3 good solid meals a day and 4 milk feeds, he is a bigger boy but well feed, hes not waking with wind, he has 2 front teeth (as of 2 weeks ago) so at first when he was waking Im sure it was teething but now that hes not teething I am unsure why hes waking, and from the of 6 weeks until 6 months he was always slept from 7pm till 7am...maybe seperation anxiety? Last night when he woke I got out of his bed but stayed in his room, gave him a cuddle and was nearly asleep in my arms, then when I put him to bed he could start crying, I did this 3 times before he would go back to sleep?? Any advise on what you think it could be and what I could do is muchly appreciated!! Thanks in advance