ANSWER - What you'd be looking at would be some type of enchantment. Theoretically possible but an enchanted object is usually an item that has had something put in it - you can imbue an object with love to invoke positivity in the recipient for example or you can work more malicious magic and spell an item to hurt someone.
To actually get an item to relay information back to you would be difficult. It would be possible to set up a kind of psychic link between you that might allow the caster some sensation of your thoughts and feelings but in terms of actually "stalking" you or getting factual information back about you via the crystal - I'm iffy about the practicalities. I'm not saying it wouldn't be beyond the capabilities of a very experienced magical practitioner but anybody with that level of power would have a very definite reason for doing so and you'd know who they were and why. This is not the kind of power that would be used for random purposes. I'd also be surprised if a crystal was chosen for this purpose - if I was attempting to cast this type of magic I would want something with a much more personal connection to you - a necklace perhaps or a piece of clothing.
If you have feelings of unease about any crystals you have purchased then a much more likely explanation is that they have picked up some negative energies and just need cleansing. Depending on what kind of crystals they are (some like selenite are water soluble so best not to get them wet) you can bury them in the earth for a few hours, wash them in moon water, lay them on a bed of quartz or smudge with sage (or any other purifying incense would work fine). If you still feel that the problem exists after cleansing then I would advise you to get rid of the crystal. Casting into the sea would be ideal but any large body of water would be a good place to rid yourself of it. Don't sell it or pass it onto anybody else because in the (highly unlikely) eventuality that the crystal has been enchanted to absorb your energies you don't want it falling into anybody else's hands.
Give it a good old cleanse and then listen to your intuition - if it still doesn't feel right then treat yourself to a trip to the seaside and chuck it.