Have you missed your period? Usually pregnancy tests are fairly accurate, but if your HCG levels are low enough then sometimes it takes a blood test to detect a pregnancy. Perhaps you should take another test or see your doctor for a blood test. If it turns out that you are not pregnant, then I don’t think it is necessary to tell your ex-boyfriend that you suspected you might have been pregnant but it turned out that you weren’t. On the other hand if it turns out that you are pregnant I think that your ex-boyfriend as the father of the child really should be told about the pregnancy. Best wishes.
Kate