Yes, it's chickweed. Get rid of it by mowing the lawn shorter and more regularly so the chickweed can't flower. Leave the mowings on the ground. Chickweed will not grow in a dense healthy lawn but needs bare soil to germinate.

That's a valiant thing to do, but you cannot possibly get every last piece of bermuda root by digging it out. Well, if you dug out an area twice the diameter and about 12 inches deep, you have a good shot at getting it all. Round Up is eventually going to be the answer. Is that a problem for you? Round Up works best on plants that are growing very well. If you fertilize a few days prior to spraying, that can help kill the plant faster. When you spray the RU, follow up with light watering every day for a week to see if you can get more to sprout. Then spray again a week later. Seeding and fertilizing a spot that used to have bermuda in an attempt to choke it out has not worked yet (in the history of lawns), so I doubt it will work for you. The problem is that fescue has too fine a blade to make enough shade to shade out (choke) the bermuda. St Augustine chokes it out every time simply by allowing the St Aug to get up to about 7 inches tall (by mowing every 2nd or 3rd week). I've been successful redoing a formerly bermuda lawn with St Aug everyplace I've tried it. I'm working on that again at a new house. At the new house I went from about 10 square feet of St Aug to 300 in a year simply by letting it go. St Aug has coarse blade structure that provides adequate shade. Fescue doesn't have that. Lets talk about crabgrass every spring. You should not be getting that. Crabgrass needs three things to germinate new seed. It needs lots of sunlight, a bare spot on the soil, and continual soil moisture for at least 3 days. Crabgrass will always start in a thin spot in full sun IF you water the lawn every day. Sunlight is not under your control. Thin spots are supposed to go away with new seed in the fall. Watering is under your control...unless you get some long term spring rain. If you only water once every 3 weeks or so (early spring), then even with a thin spot in full sun the chances of getting new crabgrass go way down. I've had three lawns in the past 25 years in San Antonio and two rural areas and have not had any crabgrass. I can't attribute that to luck. I believe it's because I actively withhold moisture. This year, 2015, I did not water at all until June. Our rain was well spaced, but that allowed the soil to dry out between drenching.

floral, Asclepias syriaca can be a prolific spreader; the other varieties are much better behaved. Kathy and the OP, If these are indeed milkweed, don't get rid of them all, as they're the plant (the only plant) on which Monarch butterflies lay their eggs. http://monarchwatch.org/bring-back-the-monarchs/campaign/the-details/

If you keep up with it, it will be gone in a couple of years. You'll always miss a few bits of rhizomes, but you'll get them later when they sprout.