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The first thing is that with an irregular cycle of 30-42 days then you may not be ovulating. The ovulation predictor kits assume a regular cycle of 24-32 days. In addition the light bleeding suggests that your uterine lining is either not thickening up during the cycle or is not being adequately shed at menstruation.
Owing to the irregular cycle, I would suggest that your see a gynecologist or fertility expert so that you can have some blood tests at day 3 and 21 of your cycle. This will show if your hormone levels are in the right level at the appropriate times of the month. You may need additional help to ovulate.
Many women do miscarry at some point when trying for pregnancy, if you had miscarried three times then we would recommend additional testing for some syndromes such as antiphospholipid syndrome which is related to recurrent miscarriage however I feel that your problem is more related to ovulation issues than auto antibodies.