Why after having my 2nd child has my dizziness and vision gotten worse?

Need workup. It is not clear why your vision worsened but please have your pcp order a brain mri. It is possible that your pituitary has enlarged due to a bleed or tumor and hence you are having compression of your visual nerves. Although rare, your complaint deserves a full workup.
Dizzy and blurry. Blurred vision can be sorted out by a refraction. Dizziness can be blood levels of sugar, blood pressure, dietary salt intake etc. Seek medical advice from competent medical professionals to help.