6 yo with violent meltdowns - help!

Hello, this is the 1st time i've been on this discussion forum, i didn't know it was here until yesterday!

I have a 6 yo son who was diagnosed with Asperger's almost a year ago. Generally, he copes brilliantly and is pretty high functioning. When he does have a meltdown though, he is violent, hitting, kicking, biting, nipping, scratching etc

This week, we've had half-term/back to school routine changes and his dad's going away pattern has changed. He's usually away from Mon pm until Thurs pm. C copes with it, though he misses him, because there's a regular pattern. This week he was here until Wednesday & will be home maybe tomorrow, maybe Mon.

I totally understand why C is all to hell & melting down but when his routine alters, he's hair trigger. He can go from calm to full meltdown in an instant and once it has begun, there's no reasoning with him. He had 2 within the space of an hour tonight, the initial trigger being not getting what he wants instantly. The thing is, he's getting too strong for me. I get out his room & leave him to calm but i have to hold his door shut to stop him coming after me. He's getting too strong for me to do this.

What do I do? We explain the changes and the reasons for it and i know he understands them intellectually although it makes no difference in practice. I asked the lady running the Cygnet course i attended recently and she had no idea either.

Thanks for reading & any suggestions gratefully received.

Rachael