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, অথবা has something serious to do with the person you're hiding it from, then আপনি should definitely tell them. However, without আরো info, that's all I can give you. If আপনি feel comfortable telling what it is, I will try to give আপনি আরো advice. If not, I hope what I did give আপনি will help.

Yes it is lying only if the intent is to deceive দ্বারা 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 চকোলেট bar from আপনি I'm not lying ,I'm just keeping it away from আপনি so আপনি can't take it away.
But if আপনি hide something that is important to আপনি and them ... well that could be lying.
in some cases worse just because when আপনি hide something important not only did আপনি hide it but আপনি also lied ...
so it just depends on how আপনি 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 আপনি outright say you're not hiding anything অথবা try to cover up whatever you're hiding in a false way, then আপনি can consider it lying.

For instance, I lied about who I was on ফ্যানপপ for...three years অথবা 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.