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Possible bed bugs my baby is being bitten please help

My 10 month old son was bitten in clusters all over his neck, this happens about every 3 months I've always thought it was mosquito bites because that's what my doctor then my mother in law suggested check for bedbugs, I checked my sons cot mattress which is brand new and I found some (I think) in the crease of his matress then checked my partner and mine bed and noticed there was little blood stains all through the bed which I had changed the weekend before similar to what I have researched please help !