Saying no?

If a guy is trying it on with you and you say no but you’re laughing while you say it so the guy continues trying it like touching you, trying to have sex, saying “come on” etc. then is that bad or is it fine since you were laughing? Like when I say no to sexual things the situation is usually quite flirty/playful so I’m like giggling and laughing so the guy thinks I’m just joking or teasing so continues to try it and like pressures me into it and it’s annoying bc I feel like it’s so hard to say no but I feel like it’s my own fault for laughing and making them think I’m being playful