Spotting?

hello everyone! I am currently on the birth control Pill and have been using it for almost 3 years. for the last 2 months I safely skipped my period. When i skipped the 2nd month, I began spotting about a week after or less. It has been continuing for about 2 weeks and i have been spotting since then. I took a test and it is negative so im not really sure what is going on. is this normal to be spotting for this long?