Everyone feels insecure or "paranoid" on occasion. I look at it as part of the "worrying cycle". It's natural to worry if someone doesn't like you because they seemed to have pulled back or stopped talking to you. And because most people aren't honest about things like that, you do wonder if the reason they are giving you is the real one. For people with anxiety or depressive issues, thoughts and feelings can be impacted in a different way, so a person may be more sensitive or irritated over things. Impacting issues can also make it tough to NOT worry about stuff.
I'm not familiar with you, so I am not sure if you are grieving your boyfriend from from a break-up or a death. My sympathies. Loss is difficult on any level, and it takes time to mourn, heal, and feel yourself again. Don't be too hard on yourself during this time. Everyone takes their own time to get past and get over things. Sometimes it's just about letting time slowly turn things around.
Your feelings of insecurity probably come in "waves", right? Some days you feel that everyone is more against you than on others. As you start to feel better from healing, your days will probably start to pick up, and you won't feel so "me against the world".
Don't stop seeing a therapist at this point!
It sounds like you could benefit from some outside guidance. Go easy on yourself and give yourself a break. You obviously are going through some things that are making you feel this way right now. If you feel your therapist isn't helping you out much any more, you should convey those feelings. Maybe you need a new therapy routine, or a different approach to your current problems. Sometimes changing the way you think or react to thoughts and circumstances can be helpful. You should tell your therapist what's going on.
Remember, on some level, we are all struggling. xo