Thanks Sangie, I started gagging about 20 minutes after I went short of breath. Thankfully it has passed now. Stoopid me Googled it afterwards and apparently it can be an early pg symptom. One site said this:
Some pregnant women do experience the feeling that they cannot catch a deep breath. This is caused by the relaxing effect of progesterone on the diaphragm and upon the accessory (helper) muscles of respiration. While it is unclear why some women experience this more acutely than others, it is a fairly common occurrence. Typically, it subsides in the first half of pregnancy.
I am highly suspicious now! I also read that some people don't create as much hCG so it takes longer to get a BFP, this may explain why I got a BFN with Kieran at 12DPO. With Joel I didn't test until a week after AF was due so I have no idea if I would have gotten an earlier BFP. I really should stop Googling and just play the waiting game LOL!