Could I be prenant - faint shadowy line on test??

I have a question, I ovulate late and my cycle can normally be anywhere from 40 to 60 days so pin pointing when period is due can be very difficult.  My hubby and I bedded 14 nights ago when I was ovulating via ‘maybe baby’ tool.  I have been feeling nauseous, tired and my need to urinate has really increased over last few days.  I took a First Reponse on what would be 9, 12 and 13 days since we bedded and they have all come up appearing negative however when held in the right light, where the positive line should be it is shadowy and has an ink mark at top and bottom of where line should be.   Do you think its possible I could be pregnant or should the lines be getting darker given the first and last 1 I have taken were 5 days apart.