Suggest Medication For Persistent Cough And Cold

im 26 weeks pregnant, have had a really persistent flemy cough (told its asthma, which i have just developed) in the past 4 - 6 days, i feel like the baby has moved right down, and evan sometimes feels like its pushing down trying to escape, it feels like she is not moving and kicking as much, and if she does move, its not the same kinda feeling and its always right down low? last night i also started seeing these wierd lights out of the corner of my eyes, maybe like what you see when a camera flashes, this lasted for about 4 - 5 mins, than had a little bit of chest pain, but i think that could be from the coughing, i have also started getting sick (vomiting) again? also was told at my last ultrasound i have low lying placenta is this normal or should i see a doctor