I really need some answers! Why are my dental implants not holding down my bottom teeth?

Implant Prosthesis. It could be related to mobility of implant fixtures, attachment mechanism wear or failure, occlusion (bite) or design with sufficient #/implants? Was this problem from the original date of insertion or did it just develop? Some issues are easily remedied ; others may not be. Your own dentist or a prosthodontist can examine you and evaluate the cause and discuss solutions.
So many reasons... So many possible reasons: 1) was the bottom teeth (your denture or partial) made with correct occlusion or fit? 2) was the amount of implant adequated for retention? 3) what was a mechanism for retention on the implant (was it a bar, an o-ring, or a locator attachment?) 4) was the position of the implant correct for load distribution? 5) were the implants placed as parallel as possible?
A few thoughts. I assume your "bottom teeth" refers to a denture. If you have only two implants, the attachments may have worn out (the "snaps" don't last forever), the denture may not fit well anymore, or something broke. This needs to be immediately evaluated by your dentist. A denture (or bridge) that does not fit will can damage the implant (s) and result in failure.
Implant Issues. It sounds like you have implant supported dentures. Implants, even though made of metal, can break. It’s uncommon, but it can happen. Also, the implants or the attachments to the dentures might have warped, or the dentures were not measured for a proper fit to begin with. The best advice is let your dentist know so they will be able to repair the damage or readjust the fit of your dentures.

Related Questions

Curious as to why are my dental implants not holding down my bottom teeth?

Many reasons! You may need to have special attachments (fasteners) replaced in the denture. Possible position of implants is a problem. Consult with your dentist, to be sure!
Worn out retention. The housing inside the denture may need to be replaced. This is an easy and inexpensive fix and should give the denure more hold. Always see your dentist 2 per year to make sure the implants stay clean.
Lower denture. I presume you have a full lower denture placed over several implants. If they snap on the implants and have started to become loose over time your dentist can replace the female attachments which are usually housed in the denture. These are usually rubber or silicone rings which can wear over time.
Denture? If you have an Overdenture with attachments on the implants, there are a few things to check. 1. Are the attachments clean from ALL debris -- both in the denture and in the mouth, 2. are the attachments in the denture deformed or crushed, 3. are the attachments old and worn out. See your dentist to evaluate. Good luck.
Connecting Component. The connecting components may have to be modified or changed to help improve the degree of retention.
Is there pain? There are great answers to the question below. I'd just like to add that if there is any pain recently than it's possible that one or several implants are failing. Look for swollen gums around the implant areas and to see if there is any movement if you touch some of the implants. Definitely see the dentist who placed/restored the implants if you can, if not then find an implant dentist.

Why are my dental implants not holding down my bottom teeth? Should I call my dentist?

Absolutely. Hard to say why the attachments are not functioning. Have your dentist take a look.
See your dentist. Impossible to adequately answer your question without more detailed info. See your dentist for evaluation. Attachments may not be clean, therefore preventing seating, or plastic may be worn out. Good Luck.
Definitely, yes. See your dentist for evaluation, proper adjustment and possible attachments replacement.