Hi there, I'm about 13.5 weeks and too have the nausea you describe. You have my sympathies!
I let go of the ideal of eating three meals a day and just go with eating what I can, even if it isn't the best food in the world. For me, that is cold food only, and normally things like plain crisps, cereal, plain yogurt, crackers, cheese spread and fruit. To reduce an awful attack of nausea, ice lollies really help! And weirdly, lemonade.
You can try those anti-sickness wrist bands from the chemist, some women find them very helpful. You can of course ask your doctor if it gets really bad.
Overall, I find what helps is small snacks when I can, and not putting pressure on myself to eat as I would normally. As long as you're taking your vitamins and eating something, the baby will get everything they need.
Hang in there. Mercifully, at 13.5 weeks, it is now easing!! X