We are sorry to hear of your miscarriage.
Unfortunately, even during this challenging period of extended niddah after a miscarriage, there are no particular leniencies at this time.
It is important to note that you may experience continued staining even after the bleeding wanes. You need not wait until the staining completely stops to start the taharah process. Once the staining is no longer reddish, you may attempt a hefsek taharah. Stains that are light brown (the color of coffee with milk) with no reddish hue are acceptable. Stains of other shades can be brought to a halachic authority for evaluation.
When birth control is required for a short period of time, the best halachically acceptable methods are spermicide or a contraceptive sponge. Both are available over the counter at the pharmacy.
Please feel free to get back to us with any further questions.
B'hatzlacha!