You are absolutely not alone! My DD was such a skimpy eater (AND nurser!) that we had nutritional concerns. She was born a hefty 8+lbs and dropped down to the 5 percentile in weight by the time she was 6 months old. She has never had a problem growing tall, but when she completely fell off the weight chart her ped asked us to get a pediatric GI and a pediatric endocrinologist involved. After all her tests came back perfect, everyone had roughly the same conclusion -- she will eat if she wants to -- but forcing her is going to create emotional stress at best -- long term eating/control issues at worst. The last thing I wanted to do was foster an unhealthy relationship with food from the get-go. So I did two things that really helped -- one, I read Child Of Mine: Feeding With Love and Good Sense by Ellyn Satter (amazing, practical, Get-Me-Through-This-NOW advice). This really helped me take the pressure off of eating/feeding times. And two -- I gave my DD eating buddies. Sitting with two other toddlers also in high chairs, watching them eat the same food really had a positive peer-pressure effect on her. It was great for my friends too to come over. I would happily provide breakfast or lunch for all the kids while the moms could have some adult time. Moms weren't hovering/stressing over every bite -- kids were being social, but engaged in eating -- it was a really positive experience. It didn't happen everyday, but it sure helped my DD figure out how to pack it in like her buddies. Now she is 20 months and 21 pounds. Still skinny -- but bouncy, happy, healthy and so tall. All specialists have given her a clean bill of health and released her from their care.
If you don't get a chance to read the Satter book, the best advice I took from it was learning feeding boundaries. It is my responsibility to decide when and what to eat -- it is my child's responsibility to put the food in her mouth and eat. Neither one of those lines should be crossed -- forcing food into a kid's mouth (which I am sorry to say I did in moments of 0 percentile desperation) over steps my boundaries. We are at a happy, healthy, control-free place with food now and it is fabulous.
Good luck and I know how hard this is. It gets better, I promise!