I had lipo and bbl done a week ago. Why do I feel so sore when I wear my faja?

Your issue is probably resolved by now as you only had to wear the faja for 2 days.  I prefer adjustable garments with multiple bands so that tension can be adjusted and the areas of liposuction are less likely to get a fluid collection. The key here is the size and the ability to tighten the garment not the brand or make. I ask my patients to wear compression garments to help obliterate dead space and reduce the incidence of fluid collections. A soft t-shirt worn under the garment makes it more comfortable to wear.Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

Hello, thanks for your question and provided information. It is completely normal to feel sore and swollen after surgery with the garment on, you need to keep doing massages, and you will be alright. 
Advantages:
One treatment may be all you need to reshape problem areas
Treat more areas—and larger areas—in one procedure
May be performed with either local or general anesthesia
More consistent and predictable result than noninvasive treatments
Liposuction, sometimes referred to as "lipo" by patients, slims and reshapes specific areas of the body by removing excess fat deposits and improving your body contours and proportion.
Different areas of treatment:
Thighs
Hips and buttocks
Abdomen and waist
Upper arms
Back
Inner knee
Chest area
Cheeks, chin and neck
Calves and ankles
Liposuction can be performed alone or along with other plastic surgery procedures, such as a facelift, breast reduction or a tummy tuck.
What liposuction can do?
Liposuction is not a treatment for obesity or a substitute for proper diet and exercise.
It is also not an effective treatment for cellulite—the dimpled skin that typically appears on the thighs, hips and buttocks—or loose saggy skin.

Thank you for your question. Swelling in the first week after this procedure is quite common. It's best to follow your surgeons specific advice post-operatively. We typically have our patients wear compression garments on the areas we did liposuction to help the skin and underlying tissues re-adhere as well as reduce swelling. However, if you garments are too tight they can restrict lymphatic drainage and blood flow leading to more swelling and complications. I'd highly suggest you contact your surgeon's office regarding your plan. Best of luck!