Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice.
In case of regular 33 days cycle you can expect ovulation around 19th day, so if conception occurred around that day you can expect
implantation bleeding from one week to 10 days after.
According to this if implantation bleeding occurred it might have occurred around ending of December or beginning of January.
If your periods are irregular we can't rule out the possibility of implantation bleeding on 25th January as you mentioned.
But as both times urine
pregnancy tests gave negative results the possibility of pregnancy is appearing less.
If you are still having symptoms, better to get evaluated to rule out the possibility of pregnancy. For that you can go for either
ultrasound which will help in ruling the out the possibility of pregnancy and also in finding the other possible causes for delay in periods, or you can go for
blood test for pregnancy that is estimation of
Beta HCG levels.
If the level is less than 5 Milli International units per ml the possibility of pregnancy is almost ruled out.
Hope I have answered your query I will be happy to answer any further follow queries.
Take care.