I went shopping nearly fainted

Michelle 🇬🇧
I was grocery shopping today and it was sooo packed in there and waiting in the long queue to put my shopping on the conveyor belt and all of a sudden I felt really faint! My legs went like jelly and my hearing gluey. I thought oh god please don't faint in front of all these people! I panicked a bit, then saw an energy drink (I'm addicted to right now) in front of my hand gripping the handle of my trolley, so I grabbed it and drank half the bottle in one go for a sugar boost. I felt better a minute or so after but that was a shock! I've never come so close to fainting in my life or ever before in my previous 3 pregnancies! Definitely different each pregnancy I tell you! (I'm 20 weeks in 2 days by the way) anyone else had fainting or feeling faint just happen?