Its normal, ive had that feeling too. Not constant but every now and then i feel that

im 25 weeks

And shes not that low at 20 weeks either even if she was you wouldnt feel pressure shes not that heavy

No that just means your babys growing. At 20 weeks babies are starting to look a little like actual babies. Dont stress it and let the pain happen. Its not gonna stay for a long time.