Hello, I have been taking vixpo birth control pills for a year. The last blood...

Hello, I have been taking vixpo birth control pills for a year. The last withdrawal bleeding occurred later than usual, but everything was okay. I am currently on the 6th tablet from the new blister and there was bleeding, even though the previous one ended 4 days ago. This month I took two antibiotics for colds – zinnat and klacid. I am currently undergoing the antibiotic klacid. Can this affect this bleeding when taking the pills? Are there grounds for concern? Thanks in advance for your reply.