If he's continuing to flirt with you, he still likes you. Flirting includes long gazes, sitting close to you, going out of his way to be near you or talk to you, trying to impress you or vie for your attention, etc. If you still worry about whether he still likes you, just ask him. Here's a suggestion for how to introduce the topic into the conversation. "John, remember what you said before winter break about your feelings for me?" (Wait for his embarrassed response.) "Do you still feel that way?" Be ready to declare how much you like him.
Little things such as complimenting him, bringing him a pack of gum or candy bar every now and then, or reaching over and drawing a heart on his notebook can be a way of showing that you care.