At dive #16 you're doing better than most to simply don a drysuit and get in the water - good on ya! Keep at it...
If you're not underweighted at the end of the dive, you're not underweighted at the beginning.
Newer divers often just have a harder time getting down. Typically finning or sculling while trying to sink; also don't hold their breath out long enough to get started and anxiety has you breathe in again too soon.
If you are shore diving - or diving off a boat with a good ladder and relatively calm seas - try entering the water without your rig and really, fully venting your suit. Then exit, don your rig and give it another go. Venting a drysuit fully - especially at the surface - isn't easy when you're new to it. Comfort, reduced anxiety, and skill will come with experience.
Ray
