Crabgrass / Weed control, Houston, TX?

Question:My grass is starting to look a little thin in spots and definitely not as green as my neighbors' lawns. Also there are some many sporadic areas of high growth of what look like weeds. They almost look like grass but with a frayed tip at the end. They grow faster than the lawn and when i mow, it feels like i am only cutting the weeds. The shaded area of my lawn is growing great, almost too fast, but is lush and green. There have been two or three times i have probably let the lawn go too long without mowing and i think the first mow of the season, i may have had the blade too low. I fertilized in the fall and spring with whatever seasonal scotts product was available. Have i waited too long to fertilize for summer? What should i put down to control this problem i am having with the weed/crabgrass? Is it too late?

Answers:
I have tried doing the fertilizing myself- but its really economical to hire a service like Scotts, or True-Green Chemlawn. They will come 4 times a year and do the necessary weed killing, fertilizing in your yard. I was paying more buying the chemicals myself. Most will give you a free estimate