Should I be worried?

I’m currently 20 weeks & 3 days pregnant. The good news is that I’ve started to put on a little bit more weight since the first trimester. The not so good news is that my weight tends to fluctuate and I’m having trouble keeping the weight on. Should I be concerned nd what kinds of things can I do to keep the weight on throughout the rest of my pregnancy (besides the obvious eating frequent meals and adding more calories)