I was in the exact same situation, except I had already night weaned. I did the acupuncture/TCM route but I"m not sure if it did anything. I also did natural progesterone cream and B6. I even ended up weaning my daughter. But, I just did "don't offer don't refuse", so she let me know if she wasn't ready since I wasn't so sure I wanted to actively wean her.
Even after weaning her, my LP was still short. I had one random 12 day LP, but the rest were no more than 10. I went to an OB and got a prescription for prometrium. The first cycle I took it, my LP was 12 days. The second cycle, I conceived, but ended up with a missed miscarriage at 8.5 weeks.
I think if I were to do it all again, I'd go straight in to get the prometrium and wouldn't wean at all. I do think that the prometrium would probably hurt my supply, but since my DD was older, I would have been ok with that.
When I took the progesterone the first month, my LP was 12 days, but I actually started spotting the last day I took the progesterone and then AF showed up the next day. I think usually, you are supposed to test the last day of the pills and if + keep taking it, if negative stop and AF will show up in a few days.
My TTC plan is to wait for my first post D&C AF and then start trying again. I really wanted my kids to be about 2 years apart. That's not how life has worked out, but I'd like to have them as close as possible, so we are going to try again ASAP.
I hope you have success with the progesterone and you are able to continue nursing.