It is less likely for meth to cause intermenstrual bleeding. These symptoms can be due to intermenstrual bleeding
may be uterine fibroids, miscarriage
after a pregnancy, ectopic pregnancy, fluctuation in hormone levels, genital infections, polyps, IUD (intrauterine device)use, use of anticoagulant drugs and hypothyroidism.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided.