What are the main problems with this diet plan?

23 year old female
Trying to lose 20 lbs

I find eating roughly the same thing daily saves me money (important) and keeps me on track. When I get tired of it, I switch it up, but here’s what I’ve been eating:

Breakfast
Smoothie with frozen mangoes, a banana, vanilla Greek yogurt, and a splash of orange juice

Lunch
Light tuna with light mayo and a few garden herb Triscuits

Snack
Nature’s Valley Protein Snack Bar

Dinner
A small portion of what I cook for my husband

I know I’m missing vegetables, but I do squeeze some in at dinner. Texture of food is a big issue for me and I can’t stand salads or most veggies, raw or cooked. I do my best to sneak them in though and keep trying new ones in case my taste buds change.

These are all quick-ish meals because I work and go to school, so I don’t have time to cook 3–5 meals daily.

I know it’s not perfect, but my eating habits have gotten out of control and any change should help. I’m just trying to break my habit of pigging out at night by staying full all day, but that doesn’t seem to be working. Should I add something to my breakfast or lunch?

I’m drinking 5–6 bottles of water daily and I’ll be starting my exercise next week – I’ll begin with walking, then stationary bike, then some light strength training.