Dachshunds need a lot more exercise than you would think - all small dogs do. She has too much energy - you know what they say - "idle hands are the devil's toolbox" or something like that. Anyway, this is so true when it comes to doggies. Tire them out and Presto! good doggie!

Try walking her briskly twice a day, or if you have time constraints, at least one longer walk per day. When you leave her in the house for now, restrict her to one quiet room or area with her bed, chew toy and water.

I agree about the walk thing. It will get rid of excess energy and mellow her out. Good time for extra training and togetherness,too.

When *anybody* "regresses", it often means there's stress of some sort, maybe emotional but often physical.

If you haven't had any changes in routine (new baby, moved from house to apt, etc), then you might want to get her a check-up.

Popping her on the butt when she's anxious & maybe sick is counter-productive to say the least.

She sounds bored. Attention and toys are a start, but exercise and mental stimulation are equally (if not more) important. A dog who's getting the right amount of exercise every day will be more likely to sleep and dream about everything he/she smelled and saw on the walks.

Every single response here has hit the nail on the head. Your dog needs to be taught who is in charge or it will take the position.
First things first. Get a regular leash, not a retractable one, and a regular choke collar not a harness and not a leather collar. Next put the collar on your dog, it should form a P. slip it on, click on the leash and go to the door. Stop. Have your dog stop and sit. When your dog is calm and all is getting bored, YOU GO OUT THE DOOR FIRST. STOP and have your dog sit again just outside the door.
Wlakies should take place every day at LEAST 3 times a day and for AT LEAST 15 minutes each walk. Take her out first thing in the morning, NO SNIFFING EVERYTHING, NO PULLING, NO GOING RIGHT TO LEFT IN FRONT OF YOU. Leash walking means your dog walks by your side and you go for a walk. The reward for this is a sniffing session for a couple of minutes AFTER the walk for bathroom duties - which should be done off your property.
Next walk should be done in th late afternoon and another on just after dinner, Ideally going out just before bedtime is a good idea as well.
Next try and find a local dog park or a place where your dog can socialize and run with other dogs. This will help wear her out. If you find a nice place, great if you can take her out once a day perfect, if just on the weekend - good enough.
Basic training should be done everyday. A SIT, STAY, DOWN AND LEAVE IT ROUTINE everyday whenever you can. Use Natural Balance meat sticks diced up as training treats. Dont worry about them drying out, the dogs will eat them like jerkey. Either refrigerate after cutting ot leave out - not in a plastic bag tho.
If you must, attach the leash of your dog to your belt, dont forget to use voice commands and positively reward your dog for good behavior.
As for your dog chewing on things it is not suppose to - this is not okay, but dont pop her on the butt, just teach her NO, and reintrodcue her to her toys in a positive manner. Your dog at 3 has reached maturity, you need to be firm or your doxie WILL start to take over your life and will no longer listen to you. PS - If you must leave the store or whever, walk your dog for a couple of minutes first and leave a puzzle toy filled with treats for her to play with while you are gone. Good luck