I wouldn't use a weighted blanket for a baby so young since it might smother him. In fact, I used to put my son to bed in a bunting made in fleece, and used no blanket at all. He only started to sleep several hours together when he was about 5 months old. The fact that he later was diagnosed with autism is purely coincidental. When my younger son, who is typically developing, was a baby, I couldn't check on him because he would wake right up when I opened the door. These are the joys of motherhood.
Autism mom since 2001.