Your Doctor will monitor you.
Don't worry.
For me, with my 2nd pregnancy... my Doctor allowed me to only gain 15 pounds total. I didn't do anything special nor limit what I ate.. I just ate healthily... and my Doctor said NO juice. For him, that is just empty calories and sugar.
No problem.
For that pregnancy, I did only gain 15 pounds total. Not even trying.
It was fine.
But my previous pregnancy, I gained 25 pounds.
Both my kids with both pregnancies, were born healthy and fine.
For you, probably water gain and retention... is adding to your overall 'weight' gain.