using blessed items for protection?

Ok I'll start with the reason I started wearing my blessed pendant from my mother.

I spent the night at my sister's apartment the other day and some very scary activity went on. I knew that there was some paranormal type of activity in the apartment before because I have heard noises there and my sister and her fiance have had similar, yet more mild, experiences that I did that night.

I used to sleep in the extra bedroom when I spent the night there but since my sister has become pregnant they are working on turning it into a nursery and with all the baby stuff just set in there for now there is no room for the guest bed. The fiance moved the mattress out to their living room for me to sleep on so I wouldn't have to sleep on the couch. I had never slept in their living room but felt ok with it. I knew before hand that most activity goes on in that room and the kitchen so I expected a little bit of noise and stuff. It ended up being much more frightening than a few knocks or footsteps though so I got very freaked out and woke my sister up since activity doesn't happen in those rooms if she is in there. She gave me a pendant from my mom that was blessed by a Catholic priest when my mother was a baby.

Since then I have been wearing it almost all the time. It makes me feel safer because I believe in God so I feel since the pendant is blessed and coincides with my beliefs that it would help protect me from harmful things like the one I encountered the other night.

My sister keeps her religious items on her bedroom wall and it seems that activity does not happen in there so we assume it is because of the religious items and the blessed cross on her wall.

I want to know if I should be wearing the pendant or if I wasn't wearing it but had it in the same room with me it would protect me? For example, when I go to bed if I were to take the necklace off and hang it next to the bed will it still have the same effectiveness as if I were wearing it? Also I was wondering if there was a way that if I accidentally did something is there possibility if would become unblessed (for lack of a better word). I have no intentions of participating in something considered "evil" or anything but was just wondering if there was a way that it could happen and if it could happen what types of things could do that?

Any insight on this would be very helpful If you want I would like to hear other peoples' experiences with using a blessed item or a sort of safety type item that would have similar protection effects.

I do know how to do the shielding and grounding through visualization but wanted to know more about this type of thing since it sort of makes me feel like I have another layer of protection around me.