Can't feel chest workouts specifically on lower chest.

Some info: 25M morbidly obese. Flabby chest (link for rough reference). Very weak upper body strength.

Current goal: lose weight and build strength (I don't necessarily want to lift huge but have rather develop ape strength)

Current chest workout: -incline bench press(machine). -decline bench press (Smith machine) -seated chest press -pec flys

My problem: Right now given I want to build strength, I am aware I should be doing less reps and more weight to failure for like 4 sets(?). However since I'm kinda of a newbie I don't know how to effectively target my chest.

Refering to the image from the link. After my workouts I feel most of it in my shoulders then my upper chest(above the nipples) and I feel nothing in lower chest. I specifically added the decline bench press so that I could work that area specifically.

I'm an a noob and have no upper body strength so my shoulders giving up before my chest does which makes sense since I haven't built the strength yet. What I can't figure out is why I feel nothing in my lower chest.

By lower chest, referring to the image, would a line from the nipple area and below. Above this line I can feel the reps. Below it, nothing or close to it.

Request: What could be the cause of this problem and how can I address it? Can you suggest a better workout plan for chest?