hai! i might be able to help. firstly, did you have this issue BEFORE you downloaded custom worlds? if not, then it's most likely related to one of your worlds.
secondly, which world are you playing in? the world from island paradise is known to have issues, so i would suggest moving elsewhere. thirdly, i would highly recommend lowering your graphics, or downloading the smooth patch mod to fix issues such as lag, slowness, etc. here's the link: GitHub - sims3fiend/Sims3SettingsSetter: Sets sims settings and stuff
disable all your mods, load the game again & then see if that has fixed the issue.
let me know if i helped in any way. :') 😃