Teeth Guinea pig keeps losing bottom teeth. Why is this?

No, pregnancy doesn't usually cause this. It sounds like a genetic issue, she should see an experienced rodent dentist, which your exotic vet can refer you to (or may be able to do himself), as they need the front teeth to keep the molars ground down. You need to ask for a top and side view x-ray, and they may give her a little anaesthetic to have a proper look inside. Your vet will probably prefer to do this once she's delivered, during pregnancy she's physically strained as is. Is she eating okay? Hay, pellets, veggies? How about drinking?

Everything is fine, she's eating, drinking, and wobbling around like she always does with her big belly! It doesn't seem to bother her but I can't help but feel bad for her.

You need to take her to see an exotic vet, it's not normal for teeth to continually grow and then fall out. @bpatters may have a better idea of what this is, but regardless you should still make an appointment.

She may have had an injury. Sometimes it takes several cycles of growing and falling out before the teeth will come in and stay in.

Or, she may lacking in calcium and/or vitamin C. That's not very likely, but it's possible, and since you haven't had her long, you don't know what her diet was like before you got her. What are you currently feeding her?

I feed her Kaytee Healthy support diet with DHA, omega 3, and probiotics. Should I switch to something else? As for vegetables I give her a couple slices of sweet bell peppers, romaine lettuce, cherry tomatoes, carrots, and occasionally she'll get a slice or two of an apple.

Kaytee pellets are crap, you should switch as soon as possible. The best brands of pellets are Oxbow and KMS Hayloft. Those veggies look pretty good to me, but make sure you're only giving her one baby carrot and one cherry tomato per day.

I figured Kaytee was a bad choice, but my mom couldn't find Oxbow and ended up buying what was there. I went to petsmart yesterday and bought oxbow hay, sadly I had no luck with finding pellets. Yes I limit the amount of carrots because of it's levels of sugars, I give them half a cherry tomato in the morning and another in the evening.

I order my pellets online. At drsfostersmith.com, a 10lb bag of Oxbow timothy pellets is only $14!

You can order KMS pellets online in bulk so you don't have to keep shopping at pet stores, it's a win-win, the best quality pellets and guilt free shopping knowing you aren't supporting anything negative! Plus KMS pellets are made with a type of calcium that's less likely to cause stone formation in your pigs.

Remember when you switch to the new pellets to make sure you do it slow or else you will upset the piggys tummy. I think there are instructions on the back of the Oxbow pellet bag about the proper way to switch to new pellets.

Oh, I didn't see that she was pregnant. Pregnant pigs should be getting extra calcium supplemented in their diet. You can do that by either providing:
–a handful per day of alfalfa hay in addition to unlimited timothy hay, and timothy pellets
–unlimited timothy hay, and alfalfa pellets
–unlimited timothy hay, timothy pellets, and 2 sprigs of parsley per day

I'll try oxbow first and kms after. Which one would you guys say is the best out of the two? the price does not matter at all to me, as long as my piggies are healthy and happy.

If the price isn't a factor, definitely go for KMS.

Switching pellets doesn't have to be done slowly. A lot of people just switch cold turkey unless the pigs go on a sit-down strike over the new ones.

You can feed more than one cherry tomato per day. Mine get 1/4 of a Roma tomato each per day, and have for years. No ill effects yet.

KMS pellets have a different calcium source than Oxbow, and pigs with urinary tract stone/sludge problems generally do well on them. If you can afford either, I'd order the KMS pellets. Be sure to choose UPS shipping, not USPS, and the price will be comparable to buying Oxbow in a local store.

Romaine can also produce excess urinary calcium, so when your pigs are at least six months old, I'd switch from that to red or green leaf lettuce.