Boyfriend using dating sites
Before you use any of the applications listed above or below, make sure that you can't be charged for illegal phone monitoring.
Look for apps that record keylogging like  which offers a free trial.
There are some that require you to install an application directly onto his phone, but there are others that will allow you to remotely-install the application to his phone if you don't have access to it.
The great Visi How article below lists some of the most popular and easiest-to-use physical-install spy applications, but if none of these work for you, you can try this application, as well: It should be noted that these remote-install spy applications are not as reliable as their physically-installed counterparts.