As a child care worker I see children of all ages go through stages of seperarion anxiety. IMO there are some children who cope better in smaller environments such as family day care which may be an option if you DS just will not settle however there are some strategies I would try first:

The things I would try first though are going to the centre with your DS and playing with him there for an hour or 2 once or twice a week for a few weeks so he can see that it's a place that you like and feel safe in. This may be enough for him to realise that day care can be a trusting place.

Making a weekly schedule for your DS with each day and what he is doing on that day. Include a photo of each activity eg monday - the park with mummy, tuesday - daycare and things he likes doing there, wednesday - playgroup etc etc. Having the visual prewarning of his routine may also help your DS to feel safer.

Good luck
HTH