A temp drop at 7dpo could be an implantation dip. Also, I don't want to get your hopes up here but cold symptoms can sometimes be an early sign of pg for some women. The body recognises the implanting bean and your immune system can drop so as to not attack it as an invader.

Whether or not it could be AF depends upon how long your LP usually is. Unless you have a 7 day LP (which is highly unusual and not at all conducive to successful implantation and should be seen to by your Dr), I wouldn't think you should be expecting AF just yet.

As for continually getting ill and not wanting to take antibiotics. You'd be far better to go and see your Dr and get over whatever is making you sick for once and for all, even if it meant taking a month or so off ttc to take medication. You are far more likely to conceive if you have a clean bill of health.

Good luck.

Lisa