In a AP, all the Nadis of your body, and your chakras, reorganize for leaving out, keeping the conection through the silver string. The brain is full os little Nadis, it takes time to reorganize them! [i have this problem too :( ] so, try to fill yourself with air (not the PHISICAL AIR, but the ASTRAL AIR). See yourself in a deep universe full of air, floating... breath making this air fill inside of you through the skin, like you were a baloon. This will make your astral body less heavy and it will make you float easy.