Help - is this a bfp or a faulty test?

Lizi • 33. Pregnant with our first.
Hi I'd be really grateful if you could help. I took this test this morning. 11dpo. My period is due in 3 days but I've had such killer back ache I thought I would test. The control line came up right away but then this second line came through faintly a few seconds after. Is this a faulty test? Thanks