I haven’t exercised a lot while pregnant and I feel so guilty now. Is it too late at 27 weeks?

I haven not exercised as much as I planned to while being pregnant. OB says my weight gain is normal: started at 152 (regular BMI) and had gained 13 lbs at 25 weeks. Now not stepping on the scale any longer because it freaks me out to see the numbers go up but today at 27 week appointment she said my weight gain was normal. Is it too late to just start walking every night? I usually walk about 20 minutes a day on my lunch break at work. I know exercise is always good, but I don’t know it will make that much of a difference now.

PS: I do eat 90% clean. Grilled chicken and vegetables almost daily for lunch and hard boiled eggs or a salad for dinner and strictly water or milk. I’m just feeling SO down on myself.