Hello and thanks for your query.
I shall make an effort to provide you with good professional recommendations specific to your questions.
It would have been better if you would have mentioned more about the symptom, like how mant days it lasted, was it like your period, amount or is it slight discharge for day or so.
Based on the information provided it is difficult to say whether you are pregnant or not.
As you have metioned that you had a protected sex, assuming this, you are less likely to be pregnant. But it is wise to see OBG specialist for your irregukarities in menses.
One of the earliest and simplest way to know that you are pregnant or not, is by using, urine
pregnancy test.
It's best to do the home pregnancy test first thing in the morning, when your urine is most concentrated and
hCG levels are highest. This test kits are nearly 98% accurate, so reliable.
I do hope that you have found something useful to help you and I shall be glad to answer any further apprehensions.
Take care and see doctor for further evaluation and help