I'm technically underweight (apparently!) don't drink nearly enough water and barely...if ever exercise..
Babies basically drain us of whatever they need! So in order to survive and grow, they'll strip us of nutrients! It's perfectly possible that your LO will be healthy despite not doing things the 'right' way because there is no right way, you can never be 100% prepared for a baby and you can never 100% follow the 'guidelines' that are about today.
Just get working on drinking more and eating healthily, ease yourself into some exercise and do the best you can from now on for you and bubs.
xx