Suspected infidelity

I'm not sure if I'm imagining this or not. In early Sept, I had a small sore on my member a couple of day after we had sex. I had my wife look at it to see what she thought about needing to have it looked at and her response was "I hope it isn't an STD." I said you have to have sexual contact to get one of those. The look on her face set me back a little, but I let it go because her education was lacking due to moving alot as a child. Then last month, she told me she was going back to her female Dr again and during her time of the month. I asked here if something was wrong because I know they don't usually want to see you then and she had done her yearly a couple of month prior. She gave me a noncommittal answer, basically agreeing with me that it was unusual, but no explanation. I again let it go. Friday I was going through the mail as I usually do and was checking an Insurance EOB. I see a $1000 charge to Ins for contraceptives from the prior month. I kind of take it hard that she didn't tell me what the deal was for a month and I had to ask what the charge was for. It was for an IUD. Her explanation is that her period flow is very bad. News to me. She is regular as an atomic clock. It is suppose to lessen this. I could accept that on its on, but all three of these things in a 3 month period is kinda hard to accept after 18 years of marriage. I haven't ever doubted my wife's fidelity before, so I'm at a loss. The coincidences just nag a me and I don't want to damage my marriage by making a false accusation. What do you think?

just be observant because people cannot hide it for long,truth eventually comes out just wait and dont jump to any conclusions it can also be some misunderstanding