Is hiding something from someone the same as lying? Is it worse?

It depends on what your hiding.
If it could hurt you, someone else, या has something serious to do with the person you're hiding it from, then आप should definitely tell them. However, without और info, that's all I can give you. If आप feel comfortable telling what it is, I will try to give आप और advice. If not, I hope what I did give आप will help.

Yes it is lying only if the intent is to deceive द्वारा withholding pertinent information.

well in a way they are different and in some ways they could be the same.
For Example if I am hiding, say, a चॉकलेट bar from आप I'm not lying ,I'm just keeping it away from आप so आप can't take it away.
But if आप hide something that is important to आप and them ... well that could be lying.
in some cases worse just because when आप hide something important not only did आप hide it but आप also lied ...
so it just depends on how आप think of it.

Lying is presenting a false statement to someone else. I do not believe lying is the same thing as hiding a truth from someone, but if आप outright say you're not hiding anything या try to cover up whatever you're hiding in a false way, then आप can consider it lying.

For instance, I lied about who I was on फैन्पॉप for...three years या so. I was hiding it from my mom, and I didn't consider it an actual "lie" until she eventually found out about it, subsequently causing me to begin logging on behind her back.

Keeping a secret isn't the same thing as "lying" in my opinion, because you're not actually telling anyone anything; you're just keeping information to yourself. However, bearing false witness to something directly to someone else is considered a lie.