what is this feeling?

34 weeks today and when walking to work to my bus stand usually have a little hill and then a two minutes walk to my bus stand. I live in the tropics so it is always hot as well.

Today when I got to the bus stand, I felt a slight heaviness on my shoulder heart rate increase , cold sweat and a bit light headed.

I checked my bp this morning and was fine and also I tried walking slow (normally a fast walker) . Not sure if I was feeling faintish since I have never fainted so any assistance will help.