Sometimes it's difficult to gauge if the person you're talking to is interested in what you're saying, which is why Psychology Today recommends listening for repeated phrases from your listener to tell if they've grown bored.
Photo by: Dave Gilbert.
Two common comments they recognise as signs of boredom are, "Oh really? That's interesting" and "That's hilarious". Neither of those are by a rule signs of boredom, but if they're being repeated a lot they might showcase your listeners disinterest. Any repeated responses are likely a warning sign, unless you happen to be blowing them away so much they can't respond with words. Find a few more tips to keep from boring your audience on Psychology Today.
7 Tips to Know If You're Boring Someone [Psychology Today]