I don't understand why I can't deadlift much weight. I am embarred. Please offer advice?

I am a 36 year old guy. I weigh 175 pounds. I have never deadlifted before. The exercises I do every other day are pull ups and chinups (5 sets of 10), push ups (100), sit ups and leg lifts (100), and bodyweight squats and lunges (50). I tried to deadlift today and all I had was 120 pounds of weights at home. I kind of struggled with 120 pounds! I did it about 15 times but it felt somewhat heavy for me. This is embarring! I see small women on youtube that weigh 115 or 125 pounds doing 250-300 pounds with hardly any effort! And many of these are good looking girly girls too. Most of them don't fit the stereotype of a big butch muscled up powerlifter woman. I thought my workout (especially the pull ups) that I have been doing for a couple year would make me strong but I guess I am very weak, especially in the lower back and in the leg muscles. How will I ever be able to deadlift more weight? There is no way as a guy I could show my face in a gym and not be able to deadlift at least my weight!