I took a 100 B-complex for a while, but it made my pee so dark yellow that it was staining my OPKs and just gross. So I switched back to a combination of 100mg B6 and 100mcg B12, in addition to my prenatal vitamin. It's obviously helping me a lot, since my LP extended from 5 day to 10 days in just three months' time. You can take up to 200mg of B6 a day without negative side effects, but I would recommend you start with a lower dosage and increase if you need to.
I also take baby aspirin, but only after I ovulate. A lot of women take it throughout their cycles, to help with blood flow to the uterus, but I have read that it can delay ovulation. Since I don't want to delay my ovulation any more than it already is, I opted to just take it after I confirm O. It will still promote blood flow to the uterus, and it's also good to take throughout the first couple of trimesters of pregnancy because it helps to prevent clots forming around the placenta.
You might also consider red raspberry leaf tea, which helps to tone the uterus. You want to stop drinking it, though, if you get pregnant. I was going to start drinking it this cycle, but I was traveling and couldn't find it. So I'm holding off until next cycle (if there is a next cycle

) to try it.