Wound not healing. I had breast reduction & lift 5 weeks ago. Is it infected? Do I need antibiotics? (Photo)

I am sorry to hear about the complication you are experiencing.  These types of complications can be quite distressing to patients;  unfortunately, sometimes the wounds do look worse before they begin to look better. The wounds tend to occur where incision lines come together (where there is the greatest tension and least blood supply).
Close follow up with your plastic surgeon will be in your best interests; sometimes removal of a exposed suture and/or removal of any unhealthy tissue will expedite healing.  As you have heard, there may be different treatment modalities recommended; best to "stick with" your plastic surgeons recommendations.
 Wound care regimens will differ from one plastic surgeon to another. Generally, this will involve application of some type of sterile dressing (in my practice I use a non-stick dressing covered by a sterile dressing for clean wounds and wet to dry dressings that  benefit from nonsurgical debridement). 
You should have peace of mind that these types of wound healing problems generally go on to heal over the course of the next several weeks, often without long-term sequelae. Also important to concentrate on a healthy diet, including good protein source.  Sometimes (depending on the width of the open wound and the appearance of the scar in the longer term), scar revision surgery may be helpful down the line. Best wishes.

What you are describing is not an uncommon issue with breast reduction surgery.  At times the area where the incisions come together (the triple point) have slow healing.  Usually this is not because of an infection and is more related to blood flow to the area which is poor.Sometimes a dose of antibiotics helps speed up the recovery of the tissue and some light debridement helps as well.  Generally antibiotic creams are applied to the area or wet-dry dressing changes are performed until the area has healed.Hope that helps.

and your surgeon needs to clean it up and start you on a wound care regimen that will facilitate healing and not simply get you out of the office.  No antibiotics needed if no spreading redness or increasing pains to suggest cellulitis as open wounds rarely if ever become 'infected'.  You have dead tissue in your wound and that all needs to be removed for your wound to start healing.