How do I know whether he loves me when he's acting like he loves me but says he doesn't?

If he really loves you he will support you through your rough times and celebrate with you through the good times, he will treat you patiently and with kindness and return you feelings. If you have any doubts it is always best to voice them however if you feel unsafe contact a family member or friend immediately

If you love him too, you should make him feel that it's alright to say that he loves you, because maybe he's scared of rejection if he voices his true feelings.

A lot of times it seems to be hard for people to share their feelings, or even recognise them. Its hard to step up and speak the words "i love you". One might not even know what love is, yet. Actions speak louder than words, if you feel loved by him all you have to do is be patient. Let him figure it out. Give him space to find the courage to open up to you. Remember, love is patient, love is kind. You are very lucky to have met love. Many people spend a whole lifetime seeking for it and never do.