Afraid..breast Milk Dried Up?

Hi Moms,
My twin babies who are 6 months now were born at 33 weeks but fortunately,not with any health issues except low birth weight.So,initially they were bottlefed at the NICU and did not latch well on breast.So, I was pumping and babies were given formula along with breastmilk.Initially,supply was good for almost 2 months and I had leakage also.Later whenever I tried to breastfeed, it felt I have small nipples and I was given nipple shield but babies did not stay on breast for long as they got used to the flow of the bottle.I feel very sad about it as I had always wanted to breasfeed.Gradually I noticed my supply was also coming down a bit less like around 40ml from both breasts together each pumping ,may be pumping doesn't give as much as bresatfeeding due to hormone production.I couldn't pump on a one month long India vacation as my breast pump didn't work there(which I didn't expect) and babies were fully formula fed for a month.I couldn't express milk manually also as electric pump only helped.When I squeezed my nipples,I could see little bit milk coming out.Has milk production dried up now coz of the one month gap and am weaning or is it because I tried pumping after long and it may take time for milk to come since I already have less supply?My periods started soon after delivery ,in almost 2.5 months.Will that also have caused reduction in supply gradually due to hormones?I really want to give my babies some breast milk atleast for some more time..