It could be mastitis, you have some of the signs. Sleeping on your tummy can block ducts if you are full at night. If you are no better in the morning I think it would be a good idea to see a doctor - or better still, give the ABA helpline a call tonight and talk it over with a counsellor who can ask more questions etc - 1800 mum 2 mum (1800 686 2 686, drop the last 6 for VOIP).