M.P.
This is a normal happening. It definitely does not mean you have a serious illness and definitely not oral cancer. Cancer presents itself as a sore or growth.
I suggest that you may never know why this year you have 5 cavities. You could have had the start of one or all of them last year but they weren't large enough to be seen. Did you have x-rays last year? I've had cavities that only showed up on an x-ray. Usually the dentist tells me I have a start of a cavity that is too small to fill now but he'll look at it next time. He fills it next time or the time after that. Once a cavity starts to form there is nothing to prevent it from growing.
I had nearly all my teeth filled by the time I was 40. Some years I had none and other years I had several. My mother had lots of cavities and was told that when she was pregnant with me she had insufficient calcium and being pregnant leached calcium out of her teeth. She did not take prenatal vits but did with her next 3 pregnancies and fared better tooth wise. Also my 3 younger brothers have very strong teeth and have had very few cavities.
Cavities are caused by many things. My teeth break off because I grind them. When a small chunk breaks off that spot is more likely to get a cavity because there is less enamel or even none at all. I suspect that the hormonal changes of pregnancy could affect our teeth. I know general health does. The cough drops leave sugar in your mouth and can cause cavities over time. It's possible that the cavities you have this year are caused by an accumulation of cough drops, skipping brushing from time to time, eating acidic foods, drinking soda pop frequently, etc.
Cavities in the front teeth are common and usually do get larger with time. I have had very small cavities between my front teeth for years and only a few years ago were they large enough to require filling.
So don't worry!!!!! Cavities alone are definitely NOT an indication of cancer or any other serious mouth condition.