New glowworm ultimate c 30 boiler losing pressure?

We have a new boiler about 8 months old but have been using it daily for about a month for heating. For the first few months it would drop to 0.4 and flash then drop to 0.0. The heating engineer from glowworm said to top up the system which we did. He said it was normal at the start. We did this roughly every 2 weeks. A month ago we started using the heating too. Since this point we need to top up the system every day. The pressure drops to 0.0 daily. Then nothing works until we top it up. I was there when it was getting fitted and we checked for any leaks then and ran the system. Any ideas?