Inability to gain weight...

Hello!

I've just come back from a two week holiday in NSW, Australia, at the beach, which was LOVELY. We did a lot of swimming, canoeing, walking and so forth, so I felt like I stayed active quite well, while being unable to access FB workouts.

Anyhow! My topic is about something else that I've been thinking about for weeks... I just can't seem to gain weight. When I first started working out, I was around 54 kg, which was the average weight for my height. However, I had no muscle and was quite flabby. Over a year later, I'm down to 46 kg, still the same height (just under 5'4") and I'm a little underweight. My body is very toned, I have great muscles and some very strong abs, but I'm a little worried I should aim to put on some more weight. People keep making remarks about how thin I am, I don't fit into most of my clothes anymore, and I also can't eat much because I get full super quick. I've had stomach issues which I think is part of the reason why I lost weight, because I constantly felt nauseous. However, things have improved (I just avoid fatty/creamy foods and that seems to help) in that area. I used to workout 5 times a week, but have slacked off in the past couple months to 2 or 3 times, but my results haven't changed at all. I even stopped working out for a few weeks and hardly anything happened (I was physically tired and stressed at that point, so it was in favour of my body). But now I'm afraid to keep working out with such ferocity when I really would rather gain weight than lose it. I'm from a large family with a tight budget, so we can't afford fancy food, and I really can't eat that much more than what I'm eating now. (I have 4 or 5 meals a day, and eat just as much as any member of my family.)

I'm not sure what to do... will I lose weight if I keep working out 4 or 5 times a week and still eating around the same? I've been on 46kg for around 5 or so months, but can't seem to bump the number up. Do you have any advice?

Thanks, guys!