BFN (5 days late)

SGlady
Hi ladies, have anyone of you encounter BFN when AF is late? I took HPT 2 days before AF and its Negative. I thought oh wells its two days before. Today i am 5 days late( my period is 32 days cycle, always came on 25th or earlier) and took a HPT last night and its negative too! 
Ps: i got UTI slightly after my Ovulation like a week after. And its gone now been 2 weeks. Eversince i have had back ache, nausea after eating and realise my areola is spreading bigger! Could i be pregnant?? Could it be because of UTI my period is delayed? Help!!