Advice Please

So this is my fourth month TTC. I had been doing OPKs months 2 and 3 and nothing so this month Indecided to start temping to try and work out if I am actually ovulating. My chart is all over the place and to be fair to me CD9-15 I was unwell - sore throat, running nose, painful sinuses and cough. I have nothing to compare my chart to but surely that impacted upon my chart. I kept temping anyways. I thought maybe I Ovulated CD16 but CD18 my temp drops again???? I am so confused. Does anyone think I ovulated? And why would I have a drop in temp if I did ovulate? TIA